JavaScript Tutorial/Statement/If — различия между версиями
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Текущая версия на 08:25, 26 мая 2010
Содержание
Conditionals
The format of a simple if statement looks like the following:
if (expression)
statement;
if...else
Syntax
if(statement){
code;
}else(statement){
code;
}
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>
Nested if statement
<html>
<head>
<title>Nested if statement</title>
<script>
var temp = 0;
temp = Math.floor(Math.random() * 100) + 1;
alert ("It"s " + temp + " degrees outside. ");
if (temp < 70){
if (temp < 30){
alert("< 30");
} else {
alert(" between 30 and 70");
}
} else {
if (temp > 85){
alert("> 85");
} else {
alert("between 85 and 70");
}
}
</script>
</head>
<body>
<h3>Hit Reload to see another temperature</h3>
</body>
</html>
Use if/else to check the returning value from a confirm dialog
<html>
<head>
<title>A Simple Page</title>
<script language="JavaScript">
<!--
var response = confirm("Do you want to proceed with this book? Click OK to proceed otherwise click Cancel.");
if ( response == true )
{
alert("A fine choice!")
}else{
alert("A not fine choice!")
}
// -->
</script>
</head>
<body>
</body>
</html>
Use if statement to check the returning value from a confirm dialog
<html>
<head>
<title>A Simple Page</title>
<script language="JavaScript">
<!--
var response = confirm("Do you want to proceed with this book? Click OK to proceed otherwise click Cancel.");
if ( response == true )
{
alert("A fine choice!");
}
// -->
</script>
</head>
<body>
</body>
</html>
Use if statement to compare the numbers
<html>
<head>
<title>Use if statement to compare the numbers</title>
<script>
var temp = 0;
var perfectTemp = 65;
temp = Math.floor(Math.random() * 100) + 1;
alert ("It"s " + temp + " degrees outside. ");
if (temp < perfectTemp){
alert("Low!!");
}
</script>
</head>
<body>
<h3>Hit Reload to see another temperature</h3>
</body>
</html>