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Tip of the Day
Language: JavaScript
Expertise: Intermediate
Aug 14, 2009

Using the Triple Equals Sign Operator (===) to Check Variable Type and Value

In some cases, the JavaScript triple equals sign operator can simplify variable type and value checking. The operator tests both type and value for equivalency. Here's a simple example HTML page that illustrates the technique.

<html>
<head></head>
<body>
<Script>
    var a=1;             // Numeric Value
    var b=1;             // Numeric Value 
    var c="1";           // String Value 
    var d="1";           //String Value 
    alert(a===b);        // Alerts 'true' as both variables are numeric,having value 1
    alert(c===d);        // Alerts 'true' as both variables are string,having value 1
    alert(b===c);        // Alerts 'false'as both variables are different type,having value 1
</script>
</body>
</html>
Aneel Maheshwari
 
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