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JavaScript DHTML/Language Basics/Variable Definition - История изменений
2026-04-04T17:41:57Z
История изменений этой страницы в вики
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http://wbex.ru/index.php?title=JavaScript_DHTML/Language_Basics/Variable_Definition&diff=3124&oldid=prev
в 09:59, 26 мая 2010
2010-05-26T09:59:54Z
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http://wbex.ru/index.php?title=JavaScript_DHTML/Language_Basics/Variable_Definition&diff=3125&oldid=prev
Admin: 1 версия
2010-05-26T07:24:30Z
<p>1 версия</p>
<p><b>Новая страница</b></p><div>==Event Handler with Multiple Statements in Attribute Value==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<TITLE>Event Handler With Multiple Statements</TITLE><br />
<SCRIPT LANGUAGE="JavaScript"><br />
<!--<br />
count=0<br />
//--><br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<H1>Event Handler With Multiple Statements</H1><br />
<P><A HREF="http://www.wbex.ru" ONMOUSEOVER="++count;<br />
alert("You moved your mouse here "+count+" times!")">Displays<br />
the number of times you move your mouse over this link.</A></P><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Get the type of a variable==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>The Typeof Example</title><br />
<script type = "text/javascript" ><br />
var aObject = {};<br />
aObject["A"] = new Object;<br />
aObject["A"].myValue = "a";<br />
document.write(typeof aObject["A"].myValue);<br />
</script><br />
</head><br />
<body><br />
</body><br />
</html><br />
<br />
<br />
</source><br />
<br />
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<br />
==Global and Local Variable Scope Demonstration==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<SCRIPT LANGUAGE="JavaScript"><br />
var globalVar = "Boy" // global<br />
var globalVar2 = "dog" // global<br />
function demo() {<br />
var globalVar2 = "cat" // local version of globalVar2<br />
var output = globalVar2 + " does not belong to " + globalVar + ".<BR>"<br />
document.write(output)<br />
}<br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<SCRIPT LANGUAGE="JavaScript"><br />
demo();<br />
document.write(globalVar2 + " belongs to " + globalVar + ".")<br />
</SCRIPT><br />
</BODY><br />
</HTML><br />
<br />
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</source><br />
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==Global scope and page scope==<br />
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<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Scope</title><br />
<script type="text/javascript"><br />
if (typeof(message) != "undefined") <br />
message += " globalPrint"; <br />
function globalPrint() {<br />
document.write(message);<br />
}<br />
</script><br />
<script type="text/javascript"><br />
function global2Print() {<br />
message += " global2Print";<br />
document.write(message);<br />
}<br />
</script><br />
<script type="text/javascript"><br />
message = "AAA";<br />
function testScope() {<br />
message += " in testScope()";<br />
document.write(message);<br />
}<br />
</script><br />
</head><br />
<body onload="testScope();global2Print();globalPrint()"><br />
<script type="text/javascript"><br />
message += " embedded in page";<br />
document.writeln(message);<br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
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<br />
==Global Versus Local Scope of a Variable==<br />
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<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Global Versus Local Scope of a Variable</title><br />
<script type="text/javascript"><br />
<!--<br />
var globalString = "A";<br />
<br />
function changeToB() {<br />
document.outputForm.beforeB.value = globalString;<br />
globalString = "B";<br />
document.outputForm.afterB.value = globalString;<br />
}<br />
<br />
function changeToC() {<br />
document.outputForm.beforeC.value = globalString;<br />
globalString = "C";<br />
document.outputForm.afterC.value = globalString;<br />
}<br />
<br />
// --><br />
</script><br />
</head><br />
<body><br />
<br />
<script type="text/javascript"><br />
<!--<br />
document.write("The initial value of globalString is \"" +Image from book globalString + "\".");<br />
// --><br />
</script><br />
<br> <form name="outputForm"><br />
<input name="changeButtonA" type="button" value="Change To B" onclick= "changeToB()"><br />
<br />
<input name="changeButtonB" type="button" value="Change To C" onclick="changeToC()"><br />
<p><br />
Value of globalString<br />
<p><br />
<input name="beforeB" type="TEXT" size="5,1"><br />
<p><br />
Before clicking on "Change To B"<br />
<p><br />
<input name="afterB" type="TEXT" size="5,1"><br />
<p><br />
After clicking on "Change To B"<br />
<p><br />
<input name="beforeC" type="TEXT" size="5,1"><br />
<p><br />
Before clicking on "Change To C"<br />
<p><br />
<input name="afterC" type="TEXT" size="5,1"><br />
<p><br />
After clicking on "Change To C"<br />
<p><br />
</form><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==String value is passed by value, while the array is passed by reference==<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 alterArgs(strLiteral, aryObject) {<br />
strLiteral = "new value";<br />
aryObject[aryObject.length] = "three";<br />
}<br />
var str = "old value";<br />
var ary = new Array("one","two");<br />
alterArgs(str,ary);<br />
document.writeln("string literal is " + str + "<br /> ");<br />
document.writeln("Array object is " + ary);<br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==The Effects of Local and Global Variables==<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 />
// Global variable modified in any function<br />
var numberA;<br />
<br />
// Global variable only modified in main script <br />
var numberB;<br />
<br />
function doubleGlobalVar(){<br />
numberA *= 2;<br />
}<br />
<br />
function tripleLocalVar() {<br />
var numberA = 1; <br />
numberA *= 3;<br />
}<br />
<br />
function doublePassedVar(numberB) {<br />
numberB *= 2;<br />
}<br />
//--><br />
</script><br />
</head><br />
<body><br />
<script type="text/javascript"> <!--<br />
numberA = 1;<br />
document.writeln("Initial value of numberA: " + numberA+"<br>");<br />
doubleGlobalVar();<br />
tripleLocalVar();<br />
document.writeln("Final value of numberA: " + numberA+"<br>");<br />
numberB = 1;<br />
document.writeln("Initial value of numberB: " + numberB+"<br>");<br />
doublePassedVar(numberB);<br />
document.writeln("Final value of numberB: " + numberB+"<br>");<br />
// --><br />
</script><br />
</body><br />
</html><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Use of Global and Local Variables==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<HTML><br />
<HEAD><br />
<TITLE>Global and Local Variables</TITLE><br />
<SCRIPT LANGUAGE="JavaScript"><!--<br />
function displaySquared(y) {<br />
var x = y * y<br />
document.write(x+"<BR>")<br />
}<br />
// --><br />
</SCRIPT><br />
</HEAD><br />
<BODY><br />
<SCRIPT LANGUAGE="JavaScript"><!--<br />
for(x=0;x<10;++x)<br />
displaySquared(x)<br />
// --><br />
</SCRIPT><br />
</BODY><br />
</HTML><br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Variable scope==<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 />
var myVar = "Outside";<br />
function testFunction() {<br />
var myVar = "Inside";<br />
alert("this.myVar: " + this.myVar);<br />
alert("myVar: " + myVar);<br />
}<br />
testFunction();<br />
//--><br />
</script><br />
</head><br />
</html><br />
<br />
<br />
<br />
<br />
</source><br />
<br />
<br />
<br />
<br />
==Variable scoping==<br />
<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="html4strict"><br />
<br />
<html><br />
<head><br />
<title>Scoping Example</title><br />
<script type = "text/javascript" ><br />
var aNewVariable = "global.";<br />
function myFunction(myPara) {<br />
document.write("Global variable within the function: " + aNewVariable);<br />
document.write("Local variable within the function: " + myPara);<br />
}<br />
</script><br />
</head><br />
<body><br />
<script type = "text/javascript" ><br />
myFunction("local");<br />
document.write("Global var outside the function: " + aNewVariable);<br />
document.write("Local var outside the function: " + myPara);<br />
<br />
</script><br />
</body><br />
</html><br />
<br />
<br />
</source></div>
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