Frequently Used Simple JavaScript Functions

RamaSagar Pulidindi
Mar 25, 2014
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Introduction

In this article we will learn some frequently used simple JavaScript functions.

Let's look at the following snippet.

String () function

The String function converts an object value to a string object. The String () function is very similar to the toString() function in JavaScript.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var today = new Date();
alert(String("Year:- " + today.getFullYear () + "Month :- " + today.getMonth()));
// January is 0
</script>
</form>
</body>
</html>

eval () function

It is used to perform the evaluation of an expression. It takes one argument and evaluates its result.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var exp = 20 + 40 - 40 + 20;
var result = eval(exp);
alert("Result is:- " + result);
</script>
</form>
</body>
</html>

isNaN () function

This function detects whether or not an object is a number. It returns true if the object is a number otherwise false.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = 20.20;
var b = 200;
var c = "Hello";
alert("a is:- " + isNaN(a) + " b is:- " + isNaN(b) + " c is:- " + isNaN(c));
</script>
</form>
</body>
</html>

Number () function

In the above example we tried to convert the Boolean type using the Number() function and it's showing “1” of the corresponding “true” value. For a string it's showing NaN, in other words it's not a number and not possible to convert it.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = true;
var b = 200;
var c = "Sagar";
alert("a is:- " + Number(a) + " b is:- " + Number(b) + " c is:- " + Number(c));
</script>
</form>
</body>
</html>

Summary

In this article we learned various frequently used global functions in JavaScript. In a future article we will learn some more basic concepts of JavaScript.