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JavaScript Tutorial/Language Basics/Variables - История изменений
2026-04-06T00:27:09Z
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http://wbex.ru/index.php?title=JavaScript_Tutorial/Language_Basics/Variables&diff=9299&oldid=prev
Admin: 1 версия
2010-05-26T08:24:57Z
<p>1 версия</p>
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Admin
http://wbex.ru/index.php?title=JavaScript_Tutorial/Language_Basics/Variables&diff=9298&oldid=prev
в 18:52, 25 мая 2010
2010-05-25T18:52:56Z
<p></p>
<p><b>Новая страница</b></p><div>== Assign one variable to another variable==<br />
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<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<html><br />
<head><br />
<title>A Simple Page</title><br />
<script language="javascript"><br />
<!--<br />
yourname = prompt("What is your name?","Type your name here ...");<br />
alert(yourname);<br />
yourname2 = yourname;<br />
alert(yourname2);<br />
yourname = prompt("Type something different in","Something different ...");<br />
alert(yourname);<br />
alert(yourname2);<br />
// --><br />
</script><br />
</head><br />
<body><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Braces indicate code blocks==<br />
<br />
<p>Code blocks indicates a series of statements that should be executed in sequence.</p><br />
<p>Code blocks are enclosed between an opening brace ({) and a closing brace (}).</p><br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
if (test1 == "red") {<br />
test1 = "blue";<br />
alert(test1);<br />
}</source><br />
<br />
<br />
<br />
== Declare two variables in the same line==<br />
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<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<html><br />
<head><br />
<title>A Simple Page</title><br />
<script language="javascript"><br />
<!--<br />
var msg1 = "Hello there", num1 = 22;<br />
alert(msg1);<br />
alert(num1);<br />
// --><br />
</script><br />
</head><br />
<body><br />
</body><br />
</html></source><br />
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<br />
== Define variable and assign value==<br />
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<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<html><br />
<head><br />
<title>Variable Demo</title><br />
<script language="javascript" type="text/javascript"><br />
<!--<br />
var myVar;<br />
myVar = "a string";<br />
alert(myVar);<br />
//--><br />
</script><br />
</head><br />
<body><br />
<h1>Variable Demo</h1><br />
</body><br />
</html></source><br />
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== Do simple calculation==<br />
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<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<HTML><br />
<BODY><br />
<SCRIPT language="JavaScript"><br />
<!--<br />
var myVar=2000;<br />
document.write(myVar+"<BR>");<br />
myVar+=2000;<br />
document.write(myVar+"<BR>");<br />
myVar=myVar-500;<br />
document.write(myVar+"<BR>");<br />
myVar=myVar*0;<br />
document.write(myVar+"<BR>");<br />
myVar=myVar+500;<br />
document.write(myVar+"<BR>");<br />
myVar-=80;<br />
document.write(myVar+"<BR>");<br />
//--><br />
</SCRIPT><br />
</BODY><br />
</HTML></source><br />
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<br />
<br />
== Naming Variables==<br />
<br />
<p>The first character of the name must be a letter or an underscore (_).</p><br />
<p>All characters following the first character can be letters, underscore, or digits.</p><br />
<p>Letters can be either upper or lowercase.</p><br />
<p>JavaScript does distinguish between the two cases.</p><br />
<p>All the following variable names are legal:</p><br />
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<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
var test;<br />
var $test;<br />
var $1;<br />
var _$te$t2;</source><br />
<br />
<br />
<br />
== Reassigning value to Variables==<br />
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<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<html><br />
<head><br />
<title>Reassigning Variables</title><br />
<script language="javascript" type="text/javascript"><br />
<!--<br />
var myVar = 3;<br />
alert("Variable myVar contains the value: " + myVar);<br />
myVar = 2;<br />
alert("Variable myVar contains the value: " + myVar);<br />
myVar = 1;<br />
alert("Variable myVar contains the value: " + myVar);<br />
myVar = "Go!";<br />
alert("Variable myVar contains the value: " + myVar);<br />
//--><br />
</script><br />
</head><br />
<body><br />
<h1>Reassigning Variables</h1><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Reference a variable without declaration==<br />
<br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<html><br />
<head><br />
<title>A Simple Page</title><br />
<script language="javascript"><br />
<!--<br />
yourname = prompt("What is your name?","Type your name here ...");<br />
alert(yourname);<br />
yourname2 = yourname;<br />
alert(yourname2);<br />
yourname = prompt("Type something different in","Something different ...");<br />
alert(yourname);<br />
alert(yourname2);<br />
// --><br />
</script><br />
</head><br />
<body><br />
</body><br />
</html></source><br />
<br />
<br />
<br />
== Variables==<br />
<br />
<p>Variables in JavaScript are defined by using the var operator (short for variable), followed by the variable name, such as:</p><br />
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<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
var test = "hi";</source><br />
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== Variables can hold different types of values at different times==<br />
<br />
<p>A variable can be initialized with a string value, and later on be set to a number value.</p><br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
var test = "hi";<br />
alert(test);<br />
test = 55;<br />
alert(test);</source><br />
<br />
<br />
<br />
== Variables don"t have to be declared before being used==<br />
<br />
<p>When the JavaScript sees a declared identifier (var varName), it creates a global variable.</p><br />
<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
var sTest = "hello ";<br />
sTest2 = sTest + "world";<br />
alert(sTest2);</source><br />
<br />
<br />
<br />
== Working With JavaScript Variables==<br />
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<br />
<br />
<br />
<!-- start source code --><br />
<br />
<source lang="javascript"><br />
<HTML><br />
<HEAD><br />
<TITLE><br />
Working With JavaScript Variables<br />
</TITLE><br />
</HEAD><br />
<BODY><br />
<H1>Working With JavaScript Variables</H1><br />
<SCRIPT LANGUAGE="JavaScript"><br />
<!--<br />
var numberOfDaysToSummer<br />
numberOfDaysToSummer = 119<br />
document.write("Number of days until summer: " + numberOfDaysToSummer + ".")<br />
// --><br />
</SCRIPT><br />
</BODY><br />
</HTML></source></div>