JavaScript DHTML/Language Basics/If
Содержание
- 1 An if..else if...else statement.
- 2 Compare int value
- 3 Compare string and alert in dialog
- 4 Compare string value in if statement
- 5 Deeply Nested if. . .else Constructions
- 6 Determining Whether Lowercase or Uppercase Strings Are "More Equal" Using an If Statement
- 7 Example for If...Else statement.
- 8 If statement
- 9 if...then...else...if
- 10 Is your input a Yes
- 11 Nested if statement, logic operator and regular expression
- 12 Nested if Statements
- 13 Nested Indented Conditional statements
- 14 Testing value in range
- 15 The else Block Responds to a false Value
- 16 Use if statement to check the value range
An if..else if...else statement.
<html>
<body>
<script type="text/javascript">
var d = new Date()
var time = d.getHours()
if (time<10){
document.write("<b>Good morning</b>")
}else if (time>10 & time<16){
document.write("<b>Good day</b>")
}else{
document.write("<b>Hello World!</b>")
}
</script>
</body>
</html>
Compare int value
<HTML>
<HEAD>
</HEAD>
<BODY>
<SCRIPT language="JavaScript">
<!--
var num1=0;
var num2=0;
if(num1==num2) {
window.alert("True");
}else {
window.alert("False");
}
//-->
</SCRIPT>
</BODY>
</HTML>
Compare string and alert in dialog
<HTML>
<HEAD>
<SCRIPT language="JavaScript">
<!--
var thesport="Golf";
var myfood="Pizza";
if(thesport=="Football"){
window.alert("Cool Sport!");
}else{
window.alert("That sport might be cool.");
}
if(myfood=="Pizza"){
window.alert("My favorite food!");
}else{
window.alert("That food sounds OK I guess.");
}
//-->
</SCRIPT>
</HEAD>
<BODY>
</BODY>
</HTML>
Compare string value in if statement
<HTML>
<HEAD>
<SCRIPT language="JavaScript">
var thesport="Golf";
if(thesport=="Football")
{
alert("Yes");
}else{
alert("No");
}
</SCRIPT>
</HEAD>
<BODY>
</BODY>
</HTML>
Deeply Nested if. . .else Constructions
<HTML>
<HEAD>
<SCRIPT LANGUAGE="JavaScript">
function testLetter(form){
inpVal = form.entry.value;
if (inpVal != "") {
if (inpVal == "A") {
alert("Thanks for the A.");
} else if (inpVal == "B") {
alert("Thanks for the B.");
} else if (inpVal == "C") {
alert("Thanks for the C.");
} else {
alert("Sorry, wrong letter or case.")
}
} else {
alert("You did not enter anything.")
}
}
</SCRIPT>
</HEAD>
<BODY>
<FORM>
Please enter A, B, or C and press Enter key:
<INPUT TYPE="text" NAME="entry" onChange="testLetter(this.form)">
</FORM>
</BODY>
</HTML>
Determining Whether Lowercase or Uppercase Strings Are "More Equal" Using an If Statement
<HTML>
<BODY>
<H1>
<SCRIPT>
if ("aa" > "AA") {
document.write("Lower case is greater than upper case!");
} else if ("hogwarts" == "HOGWARTS") {
document.write("They are the same!");
} else {
document.write("Upper case is greater than lower case!");
}
</SCRIPT>
</H1>
</BODY>
</HTML>
Example for If...Else statement.
<html>
<body>
<script type="text/javascript">
var d = new Date()
var time = d.getHours()
if (time < 10) {
document.write("<b>Good morning</b>")
}else{
document.write("<b>Good day</b>")
}
</script>
</body>
</html>
If statement
<html>
<body>
<script type="text/javascript">
var d = new Date()
var time = d.getHours()
if (time < 10) {
document.write("<b>Good morning</b>")
}
</script>
</body>
</html>
if...then...else...if
<html>
<head>
<title>if...then...else...if</title>
<script type="text/javascript">
var stateCode = "MO";
if (stateCode == "OR") {
taxPercentage = 3.5;
} else if (stateCode == "CA") {
taxPercentage = 5.0;
} else if (stateCode == "MO") {
taxPercentage = 1.0;
} else {
taxPercentage = 2.0;
}
document.write(taxPercentage);
</script>
</head>
<body>
</body>
</html>
Is your input a Yes
<html>
<head>
<title>Confirming Something</title>
<script type = "text/javascript">
function processConfirm(answer) {
var result = "";
if (answer) {
result = "Yes";
} else {
result = "No";
}
return result;
}
</script>
</head>
<body>
<script type = "text/javascript">
var confirmAnswer = confirm("Yes or no?");
var theAnswer = processConfirm(confirmAnswer);
document.write(theAnswer);
</script>
</body>
</html>
Nested if statement, logic operator and regular expression
<html>
<head>
<title></title>
</head>
<body>
<script type = "text/javascript" >
var inputNum = prompt("Please enter a number between 50 and 100:");
if (isNaN(inputNum)) {
if (inputNum.match(/one|two|three|four|five|six|seven|eight|nine|ten/)) {
document.write("it is in English");
} else {
document.write(" not a number.");
}
}
else if ((inputNum > 99) || (inputNum < 51)) {
document.write(inputNum + ", is not between 50 and 100.");
}
</script>
</body>
</html>
Nested if Statements
<html>
<head>
<title>Nested if Statements</title>
</head>
<body>
<script type="text/javascript">
<!--
var needsInfo;
var needsMoreInfo;
needsInfo = true;
needsMoreInfo = true;
if (needsInfo) {
document.writeln("info true");
if(needsMoreInfo){
document.write("<br>needs info true");
}
document.writeln("<br>Ordering is easy using our on-line service.");
}
// -->
</script>
</body>
</html>
Nested Indented Conditional statements
<html>
<head>
<title>Nested Indented Conditional statements</title>
<script type="text/javascript">
var prefChoice = 1;
var stateChoice = "R";
var genderChoice = "F";
if (prefChoice == 1) {
if (stateChoice == "R") {
if (genderChoice == "M") {
document.write("...");
}
}
}
</script>
</head>
<body>
</body>
</html>
Testing value in range
<html>
<head>
<title>Testing value in range</title>
<script type="text/javascript">
var nValue = 0;
if (nValue >= 0 && nValue <= 100) {
alert("value between 0 and 100, inclusive");
} else if (nValue > 0 && nValue < 100) {
alert("value between 0 and 100 exclusive");
} else if (nValue > 100) {
alert ("value over 100");
} else if (nValue > 0) {
alert ("value is negative");
}
</script>
</head>
<body>
</body>
</html>
The else Block Responds to a false Value
<html>
<head>
<title>The else Block Responds to a false Value</title>
</head>
<body>
<script type="text/javascript">
<!--
var purchaseAmount;
purchaseAmount = 101.00;
if(purchaseAmount > 500.00){
document.write("Thank you for your purchase!");
}else{
document.writeln("Thank you, but surely there is something ");
}
// -->
</script>
</body>
</html>
Use if statement to check the value range
<html>
<head>
<title></title>
</head>
<body>
<script type="text/javascript">
var temp = prompt("number value:");
if (temp > 100) {
document.write("100");
} else if (temp < 20) {
document.write("20");
}
</script>
</body>
</html>