http://wbex.ru/index.php?action=history&feed=atom&title=JavaScript_DHTML%2FLanguage_Basics%2FFunction
JavaScript DHTML/Language Basics/Function - История изменений
2026-04-04T21:31:29Z
История изменений этой страницы в вики
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http://wbex.ru/index.php?title=JavaScript_DHTML/Language_Basics/Function&diff=3122&oldid=prev
в 09:59, 26 мая 2010
2010-05-26T09:59:54Z
<p></p>
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<td colspan="1" style="background-color: white; color:black; text-align: center;">← Предыдущая</td>
<td colspan="1" style="background-color: white; color:black; text-align: center;">Версия 09:59, 26 мая 2010</td>
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http://wbex.ru/index.php?title=JavaScript_DHTML/Language_Basics/Function&diff=3123&oldid=prev
Admin: 1 версия
2010-05-26T07:24:30Z
<p>1 версия</p>
<p><b>Новая страница</b></p><div>==Accepting Either One or No Arguments==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>JavaScript Unleashed</title><br />
<script type="text/javascript"><br />
<!--<br />
function welcomeMessage(userName) {<br />
if (userName != null) {<br />
document.writeln("Hello, " + userName);<br />
}else{<br />
document.write("variable \"userName\" would show : ");<br />
document.writeln(userName);<br />
}<br />
}<br />
// --><br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
<!--<br />
document.writeln("First call to welcomeMessage(),\n");<br />
welcomeMessage("Mr.");<br />
document.writeln("<HR>\nSecond call to welcomeMessage(),\n");<br />
welcomeMessage();<br />
// --><br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==A Function Can Be Set Up to Accept a Variable Number of Arguments==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>A Function Can Be Set Up to Accept a Variable Number of Arguments</title><br />
<script type="text/javascript"><br />
<!--<br />
function welcomeMessage(userName) {<br />
if (userName != null) {<br />
document.writeln("Hello, " + userName);<br />
}else{<br />
document.writeln("Welcome to our Web site!");<br />
}<br />
numArgs = welcomeMessage.arguments.length;<br />
if(numArgs > 1) {<br />
for(var i = 1; i < numArgs; i++) {<br />
document.writeln("\""+welcomeMessage.arguments[i]+"\"");<br />
}<br />
}<br />
}<br />
// --><br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
<!--<br />
var userName = "David", extraMsg = "It has been a long time!";<br />
var userName2 = null;<br />
var extraMsg1 = "Would you like to become a member?";<br />
var extraMsg2 = "You can enroll online!";<br />
welcomeMessage(userName, extraMsg);<br />
document.writeln("<hr>"); welcomeMessage(userName2, extraMsg1, extraMsg2);<br />
// --><br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==A Function Definition==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<TITLE>A function definition</TITLE><br />
<SCRIPT LANGUAGE="JavaScript"><!--<br />
function displayTaggedText(tag, text) {<br />
document.write("<"+tag+">")<br />
document.write(text)<br />
document.write("</"+tag+">")<br />
}<br />
// --><br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<SCRIPT LANGUAGE="JavaScript"><!--<br />
displayTaggedText("H1","This is a level 1 heading")<br />
displayTaggedText("P","This text is the first paragraph of the document.")<br />
// --><br />
</SCRIPT><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==A Function"s arguments and caller Properties==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
/*<br />
JavaScript Bible, Fourth Edition<br />
by Danny Goodman <br />
John Wiley & Sons CopyRight 2001<br />
*/<br />
<HTML><br />
<HEAD><br />
<SCRIPT LANGUAGE="JavaScript"><br />
function hansel(x,y) {<br />
var args = hansel.arguments<br />
document.write("<P>hansel.caller is " + hansel.caller + "<BR>")<br />
document.write("hansel.arguments.length is " + hansel.arguments.length + "<BR>")<br />
for (var i = 0; i < args.length; i++) {<br />
document.write("argument " + i + " is " + args[i] + "<BR>")<br />
}<br />
document.write("</P>")<br />
}<br />
function gretel(x,y,z) {<br />
today = new Date()<br />
thisYear = today.getFullYear()<br />
hansel(x,y,z,thisYear)<br />
}<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<SCRIPT LANGUAGE="JavaScript"> <br />
hansel(1, "two", 3);<br />
gretel(4, "five", 6, "seven");<br />
</SCRIPT><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==A function with arguments, that returns a value==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<br />
<html><br />
<head><br />
<script type="text/javascript"><br />
function total(a,b){<br />
return a + b<br />
}<br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
document.write(total(2,3))<br />
</script><br />
<br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==A function with only one statement==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>A Simple Page</title><br />
<script language="JavaScript"><br />
function yourMessage()<br />
{<br />
alert("Your first function!");<br />
}<br />
</script><br />
</head><br />
<body><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Array filter and callback functions==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Array filter and callback functions</title><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
function checkColor(element,index,array) {<br />
return (element >= 0 && element < 256);<br />
}<br />
var colors = new Array( );<br />
colors[0] = [0,262,255];<br />
colors[4] = [0,0,255];<br />
colors[5] = [-5,567,255];<br />
var testedColors = new Array( );<br />
for (var i in colors) {<br />
testedColors[i] = colors[i].filter(checkColor);<br />
document.write(testedColors[i]);<br />
}<br />
<br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Call a javascript function with javascript:void()==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Void</title><br />
</head><br />
<body><br />
<p><a href="javascript:void(window.open("http://www.google.ru/"))"><br />
Click here to open a new window.</a></p><br />
</body><br />
</html><br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Call function in body onload event==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Random Quote</title><br />
<script type="text/javascript"><br />
function getQuote() {<br />
document.write("onload");<br />
}<br />
</script><br />
</head><br />
<body onload="getQuote();"><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Calling a Function from an Event Handler==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<SCRIPT LANGUAGE="JavaScript"><br />
function showMsg(msg) {<br />
alert("The button sent: " + msg)<br />
}<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<FORM><br />
<INPUT TYPE="button" VALUE="Click Me" <br />
onClick="showMsg ("The button has been clicked!")"><br />
</FORM><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Calling a Generalizable Function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<TITLE>Variable Scope Trials</TITLE><br />
<SCRIPT LANGUAGE="JavaScript"><br />
function factorial(n) {<br />
if (n > 0) {<br />
return n * (factorial(n - 1));<br />
} else {<br />
return 1;<br />
}<br />
}<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<FORM><br />
Enter an input value: <INPUT TYPE="text" NAME="input" VALUE=0><br />
<P><INPUT TYPE="button" VALUE="Calc Factorial" <br />
onClick="this.form.output.value = factorial(this.form.input.value)"><br />
<P>Results: <INPUT TYPE="text" NAME="output"><br />
</FORM><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Call your function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>A Simple Page</title><br />
<script language="JavaScript"><br />
yourMessage();<br />
function yourMessage()<br />
{<br />
alert("Your first function!");<br />
}<br />
</script><br />
</head><br />
<body><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Check the function parameters==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<head><br />
<title></title><br />
<script type = "text/javascript" ><br />
function addNums(firstNum,secondNum) {<br />
if ((isNaN(firstNum)) || (isNaN(secondNum))) {<br />
alert("Arguments must be numbers.");<br />
return;<br />
}<br />
else if (firstNum > secondNum) {<br />
alert(firstNum + " is greater than " + secondNum);<br />
}<br />
else {<br />
return firstNum + secondNum;<br />
}<br />
}<br />
</script><br />
</head><br />
<body><br />
<script type = "text/javascript" ><br />
document.write(addNums("aaa",3));<br />
document.write("<BR>");<br />
document.write(addNums(2,3));<br />
</script><br />
</body><br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Declaring a Function in the "head" Block==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>JavaScript Unleashed</title><br />
<script type="text/javascript"><br />
<!--<br />
function defaultColors() {<br />
document.writeln("Inside of defaultColors()");<br />
document.fgColor = "black";<br />
document.bgColor = "white"; <br />
}<br />
// --><br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
<!-- <br />
document.writeln("Functions are scripts just waiting to run!");<br />
defaultColors();<br />
document.writeln("All done.");<br />
// --><br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Define a function to accept the string value==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>My First Page</title><br />
<script type = "text/javascript"><br />
function myFunc(textToAlert) {<br />
alert(textToAlert);<br />
}<br />
myFunc("This is a test");<br />
</script><br />
</head><br />
<body><br />
</body><br />
</html><br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Define function in JavaScript==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<script type="text/javascript"><br />
function myfunction(){<br />
alert("HELLO")<br />
}<br />
</script><br />
</head><br />
<body><br />
<form><br />
<input type="button" onclick="myfunction()" value="Call function"><br />
</form><br />
<br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Funciton with arguments==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<script type="text/javascript"><br />
function myfunction(txt){<br />
alert(txt)<br />
}<br />
</script><br />
</head><br />
<body><br />
<form><br />
<input type="button" onclick="myfunction("Hello")" value="Call function"><br />
</form><br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Function is Object==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Function Object</title><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
function funcObject(x,y,z) {<br />
for (var i = 0; i < funcObject.length; i++) {<br />
document.writeln("argument " + i + ": " + arguments[i] + "<br />");<br />
}<br />
}<br />
funcObject(1,2,3);<br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Functions That Return Values Can Be Used in Expressions==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
/*<br />
JavaScript Unleashed, Third Edition<br />
by Richard Wagner and R. Allen Wyke <br />
ISBN: 067231763X<br />
Publisher Sams CopyRight 2000<br />
*/<br />
<br />
<html><br />
<head><br />
<title>JavaScript Unleashed</title><br />
<script type="text/javascript"><br />
<!--<br />
function isPhone(aString) {<br />
var aChar = null;<br />
var status = true;<br />
if(aString.length != 13) {<br />
status = false;<br />
}else{<br />
for(var i = 0; i <= 12; i++) {<br />
aChar = aString.charAt(i);<br />
if ( i == 0 && aChar == "(" ){<br />
continue;<br />
}else{<br />
if( i == 4 && aChar == ")" ){<br />
continue;<br />
}else{<br />
if( i == 8 && aChar == "-" ){<br />
continue;<br />
}else{<br />
if( parseInt(aChar,10) >= 0 && parseInt(aChar,10) <= 9 ){<br />
continue;<br />
}else {<br />
status = false;<br />
break;<br />
}<br />
}<br />
}<br />
}<br />
}<br />
}<br />
return(status);<br />
}<br />
// --><br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
<!--<br />
var userInput = "(800)555-1212"; <br />
<br />
if(isPhone(userInput)) {<br />
document.writeln("Thank you for your phone number.");<br />
document.writeln("I will have a representative get you");<br />
document.writeln("more information.");<br />
}else{<br />
document.writeln("Please re-enter your phone number");<br />
document.writeln("using the format (###)###-####");<br />
}<br />
//--><br />
</script><br />
<br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Function that returns a value==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<script type="text/javascript"><br />
function myFunction(){<br />
return ("Hello!")<br />
}<br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
document.write("return from function")<br />
document.write(myFunction())<br />
</script><br />
<br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Function That Wraps Document.Write, Adding a Line Break==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<BODY><br />
<CENTER><br />
<H1><br />
<SCRIPT> <br />
function myFunction (textIn) { <br />
document.write (textIn + "<br>"); <br />
} <br />
myFunction ("I"); <br />
myFunction ("did"); <br />
myFunction ("it"); <br />
myFunction ("my"); <br />
myFunction ("way!"); <br />
</SCRIPT><br />
</CENTER><br />
</H1><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Invoking third argument as function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Pass Me</title><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
function funcObject(x,y,z) {<br />
alert(z(x,y));<br />
}<br />
// third parameter is function<br />
funcObject(1,2,function(x,y) { return x * y});<br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Nested function call==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>A Simple Page</title><br />
<script language="JavaScript"><br />
function firstMessage(){<br />
alert("A");<br />
secondMessage();<br />
alert("B");<br />
}<br />
function secondMessage()<br />
{<br />
alert("another function");<br />
}<br />
</script><br />
</head><br />
<body onLoad="firstMessage()"><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Passing by Reference Versus Passing by Value==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
/*<br />
JavaScript Unleashed, Third Edition<br />
by Richard Wagner and R. Allen Wyke <br />
ISBN: 067231763X<br />
Publisher Sams CopyRight 2000<br />
*/<br />
<html><br />
<head><br />
<title>JavaScript Unleashed</title><br />
<script type="text/javascript"><br />
<!--<br />
// wrap and integer inside an object<br />
function intObject() {<br />
this.i;<br />
return this;<br />
}<br />
<br />
function start() {<br />
// declare two ways to store an integer<br />
var I;<br />
var myIntObject = new intObject();<br />
<br />
// assign initial values<br />
i = 0;<br />
myIntObject.i = 0;<br />
<br />
// display current values<br />
document.write("<br>Before<br>");<br />
document.write("i = " + i);<br />
document.write("<br>");<br />
document.write("myIntObject = " + myIntObject.i);<br />
document.write("<br>");<br />
<br />
// pass variables<br />
modify(i, myIntObject);<br />
<br />
// display current values<br />
document.write("<br>After<br>");<br />
document.write("i = " + i);<br />
document.write("<br>");<br />
document.write("myIntObject = " + myIntObject.i);<br />
document.write("<br>");<br />
} <br />
function modify(n, obj) {<br />
n++;<br />
obj.i++;<br />
}<br />
//--><br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
<!--<br />
start();<br />
//--><br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Passing the Form Object as a Parameter==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<TITLE>Beatle Picker</TITLE><br />
<SCRIPT LANGUAGE="JavaScript"><br />
function processData(form) {<br />
for (var i = 0; i < form.items.length; i++) {<br />
if (form.items[i].checked) {<br />
break<br />
}<br />
}<br />
var choseItem = form.items[i].value<br />
var chosenSong = form.song.value<br />
alert("Looking to see if " + chosenSong + " was written by " + choseItem + "...")<br />
}<br />
function checkSong(songTitle) {<br />
var enteredSong = songTitle.value<br />
alert("Making sure that " + enteredSong + " was recorded by the items.")<br />
}<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<FORM NAME="Abbey Road"><br />
Choose your favorite Beatle:<br />
<INPUT TYPE="radio" NAME="items" VALUE="A" CHECKED="true">A<br />
<INPUT TYPE="radio" NAME="items" VALUE="B">B<br />
<INPUT TYPE="radio" NAME="items" VALUE="C">C<br />
<INPUT TYPE="radio" NAME="items" VALUE="D">D<br />
<P><br />
Enter the name of your favorite items song:<BR><br />
<INPUT TYPE="text" NAME="song" VALUE="value" onChange="checkSong(this)"><P><br />
<INPUT TYPE="button" NAME="process" VALUE="Process Request..." onClick="processData(this.form)"><br />
</FORM><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Pass string value in and return string value out==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<br />
<HTML><br />
<HEAD><br />
<SCRIPT language="JavaScript"><br />
function myFunc(my, p)<br />
{<br />
alert(my + " : " + p);<br />
} <br />
function get_added_text() <br />
{<br />
var textpart1 = "A ";<br />
var textpart2 = "B";<br />
var added_text = textpart1 + textpart2;<br />
return added_text;<br />
}<br />
myFunc("A",1500);<br />
var alert_text=get_added_text();<br />
window.alert(alert_text);<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Pass variables to a function, and use these variable values in the function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html> <br />
<head> <br />
<script type="text/javascript"> <br />
function myfunction(txt){ <br />
alert(txt) <br />
} <br />
</script> <br />
</head> <br />
<body> <br />
<form> <br />
<input type="button" onclick="myfunction("Java!")" value="Java"> <br />
<input type="button" onclick="myfunction("Java too!")" value="Java too"> <br />
</form> <br />
</body> <br />
</html> <br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Return an incremented value==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<head><br />
<title></title><br />
<script type = "text/javascript" ><br />
function incrementNum(myNum) {<br />
if (isNaN(myNum)) {<br />
alert(myNum + " isn"t a number.");<br />
return;<br />
}<br />
return myNum + 1;<br />
}<br />
</script><br />
</head><br />
<body><br />
<script type = "text/javascript" ><br />
alert(incrementNum(3));<br />
</script><br />
</body><br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Save returned value from a function to a variable==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<head><br />
<title></title><br />
</head><br />
<body><br />
<script type = "text/javascript" ><br />
function addNumbers() {<br />
firstNum = 4;<br />
secondNum = 8;<br />
result = firstNum + secondNum;<br />
return result;<br />
}<br />
result = 0;<br />
alert(result);<br />
sum = addNumbers();<br />
alert(result);<br />
</script><br />
</body><br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==setTimeout() with a pointer to a function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<script type="text/javascript"><br />
function timeout(){<br />
window.setTimeout("show_alert()",2000)<br />
}<br />
function show_alert(){<br />
alert("hi")<br />
}<br />
</script><br />
</head><br />
<body><br />
<form><br />
<input type="button" onclick="timeout()" value="Count down"><br />
</form><br />
</body><br />
</html><br />
<br />
////////////////////////////////////////<br />
Hi Sirs/Madams of wbex.ru,<br />
<br />
I came across an article on your site about "pointers to a function in<br />
javascript", in use with setTimeout*.<br />
Well, that very title shows you do not understand th parts of<br />
javascript you are talking about well enough. However, when actually<br />
reading the article it is revealed that your misunderstanding goes<br />
even deeper.<br />
That"s why I decided to send you this email and learn you a thing or<br />
two about javascript.<br />
<br />
First off, your example resorts to the use of setTimeout("show_alert()", 4000).<br />
Obviously you are passing a string, not a pointer to a function. Now<br />
there are two ways to call setTimeout, one with a string and one with<br />
a function. The last version is pretty much like using a pointer to a<br />
function, but there are some differences. However, when using that<br />
title the correct way to call setTimeout, would have been<br />
"setTimeout(show_alert, 4000)". And yes, it would actually have had<br />
the same result as the given code. Also, do note that tis circumvents<br />
the indirect usage of eval (which you probably know is evil), as eval<br />
is what is used to make sense of the string that can be passed to<br />
setTimeout.<br />
<br />
Now as for function pointers in javascript. Javascript does not know<br />
any pointers. This includes function pointers. However, this is no<br />
loss, because javascript functions are different things than functions<br />
are in most languages.<br />
In javascript functions are values, just like numbers, booleans and<br />
objects are. They can be treated as such in every respect and<br />
additionally you can call them. As such, you can have function<br />
constants. These are commonly known as anonymous functions and look<br />
like this:<br />
<br />
function (args) {/*body*/}<br />
<br />
It also means you can assign a function value to a variable. Logically<br />
this looks like this:<br />
<br />
var variable = function (args) {/*body*/}<br />
<br />
And now for the real magic of javascript, this line above is the real<br />
meaning of the standard way to declare a function. Confused? Let me<br />
show you:<br />
<br />
function functionName (args) {/*body*/}<br />
<br />
does the exact same thing as:<br />
<br />
var functionName = function (args){/*body*/}<br />
<br />
This alternate syntax was simply added to have the functions appear to<br />
work as in other languages, but as you have jut seen, they do work<br />
slightly different. However, this way in which they do work is a more<br />
powerful way. For example, we do not need a concept such as a function<br />
pointer, we can simply require an argument to be a function. From<br />
there on, a programmer can decide to supply a variable which holds a<br />
function (the thing I did above in your sample), or one can decide to<br />
supply a function literal. In that case you example would look like<br />
this:<br />
<br />
function timeout()<br />
{<br />
setTimeout(function()<br />
{<br />
alert("hi");<br />
}, 4000);<br />
}<br />
<br />
Of course, the spacing could be altered to put all of this on one line.<br />
<br />
I hope I taught you a little about javascript and I hope this may<br />
serve as a way to decrease the amount of faulty information about the<br />
intricacies of javascript in the top results of google search.<br />
<br />
Yours sincerely,<br />
<br />
Jasper Horn<br />
jasperhorn at gmail.ru<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Show Arguments==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<script><br />
<!--<br />
function showArgs(a, b, c) {<br />
var argList = "";<br />
for (var n=0; n <= arguments.length; n++) {<br />
argList += n + ". " + arguments[n] + "\n";<br />
}<br />
alert(argList);<br />
}<br />
showArgs("java", "script");<br />
//--><br />
</script><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Simplest function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<script language="JavaScript"><br />
<!--<br />
function TestFunction() {<br />
var localVar = "Hello";<br />
}<br />
alert(localVar);<br />
//--><br />
</script><br />
</head><br />
</html><br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Using an Argument with a JavaScript Function==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>JavaScript Unleashed</title><br />
</head><br />
<body><br />
<script type="text/javascript"><br />
<!-- <br />
function getBinary(anInteger) {<br />
var result = "";<br />
var shortResult = "";<br />
for(var i=1; i <= 32; i++) {<br />
if(anInteger & 1 == 1) {<br />
result = "1" + result;<br />
shortResult = result;<br />
} else { <br />
result = "0" + result;<br />
}<br />
anInteger = anInteger >> 1;<br />
}<br />
return(shortResult);<br />
}<br />
var binaryString = "";<br />
<br />
x = 127;<br />
binaryString = getBinary(x);<br />
<br />
document.write("The number " + x + " in binary form is : \n");<br />
document.writeln(binaryString);<br />
<br />
x = 255;<br />
binaryString = getBinary(x);<br />
<br />
document.write("The number " + x + " in binary form is : \n");<br />
document.writeln(binaryString);<br />
document.writeln("The variable x is still equal to : " + x);<br />
// --><br />
</script><br />
<br />
</body><br />
</html><br />
<br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Using the Function Object==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<TITLE>Using the Function Object</TITLE><br />
<BODY><H1><br />
<SCRIPT LANGUAGE="JavaScript"><!--<br />
addBraces = new Function("s","return "["+s+"]"")<br />
document.write(addBraces("This"))<br />
document.write(addBraces("is"))<br />
document.write(addBraces("a"))<br />
document.write(addBraces("test."))<br />
// --></SCRIPT><br />
</H1></BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Variable Scope Workbench Page==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
/*<br />
JavaScript Bible, Fourth Edition<br />
by Danny Goodman <br />
John Wiley & Sons CopyRight 2001<br />
*/<br />
<HTML><br />
<HEAD><br />
<TITLE>Variable Scope Trials</TITLE><br />
<SCRIPT LANGUAGE="JavaScript"><br />
var headGlobal = "Gumby"<br />
function doNothing() {<br />
var headLocal = "Pokey"<br />
return headLocal<br />
}<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<SCRIPT LANGUAGE="JavaScript"><br />
// two global variables<br />
var aBoy = "Charlie Brown"<br />
var hisDog = "Snoopy"<br />
function testValues() {<br />
var hisDog = "Gromit" // initializes local version of "hisDog"<br />
var page = ""<br />
page += "headGlobal is: " + headGlobal + "<BR>"<br />
// page += "headLocal is: " + headLocal + "<BR>" // : headLocal not defined<br />
page += "headLocal value returned from head function is: " + doNothing() + "<P>"<br />
page += " aBoy is: " + aBoy + "<BR>" // picks up global<br />
page += "local version of hisDog is: " + hisDog + "<P>" // "sees" only local<br />
document.write(page)<br />
}<br />
testValues()<br />
document.write("global version of hisDog is intact: " + hisDog)<br />
</SCRIPT><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
<br />
<br />
</source></div>
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