In this article we will learn four very important and frequently used global function in JavaScript.
In this article we will learn four very important global functions in JavaScript. The term global means, we can call and implement those function in any JavaScript program and from anywhere of the program. Those functions are written in library. Let’s understand them one by one.
String() function
String function is used to convert the object value to
string object. The String() function is very much similar with toString()
function in JavaScript. Here is sample code example of String function.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="JavaScript.aspx.cs" Inherits="JavaScript.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()));
</script>
</form>
</body>
</html>
In this example we are getting full year and month from data
object then we are converting them as string and concatenating with some other
string. Here is output.
eval() function
evl() function is used to perform the evaluation of
expression. It takes one argument and evaluate it’s result. Have a look on
below code.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="JavaScript.aspx.cs" Inherits="JavaScript.JavaScript" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var exp = 10 + 30 - 30 + 10;
var result = eval(exp);
alert("Result is:- " + result);
</script>
</form>
</body>
</html>
In this example we are evaluating one mathematical
expression using eval() function. Here is output
isNaN() function
This function is used to detect whether one object is number
or not. It returns true if the object is a number otherwise return false. We
will implement one example with isNaN() function.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="JavaScript.aspx.cs" Inherits="JavaScript.JavaScript" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = 10.10;
var b = 100;
var c = "Hello";
alert("a is:- " + isNaN(a) + " b is:- " + isNaN(b) + " c is:- " + isNaN(c));
</script>
</form>
</body>
</html>
Here a and b are number but c is not . So that in case of c
it’s showing true, means it’s not a number.
Number() function
When there is need to get corresponding number value (if
possible) of certain object, we can use Number() function. Try to understand
below code.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="JavaScript.aspx.cs" Inherits="JavaScript.JavaScript" %>
<!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 = 100;
var c = "Sourav";
alert("a is:- " + Number(a) + " b is:- " + Number(b) + " c is:- " + Number(c));
</script>
</form>
</body>
</html>
In above example we have tried to convert Boolean type using
Number() function, and it’s showing “1” of corresponding “true” value. In case
of string it’s showing NaN, means it’s not a number and not possible to
convert.
Conclusion
In this example we have learned four different global functions
in JavaScript. Those are very much needed in real time application development.
Hope you have understood them.