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.
  1. <!DOCTYPE html>
  2. <html xmlns="http://www.w3.org/1999/xhtml">
  3. <head runat="server">
  4. </head>
  5. <body>
  6. <form id="form1" runat="server">
  7. <script>
  8. var today = new Date();
  9. alert(String("Year:- " + today.getFullYear () + "Month :- " + today.getMonth()));
  10. // January is 0
  11. </script>
  12. </form>
  13. </body>
  14. </html>

eval () function

It is used to perform the evaluation of an expression. It takes one argument and evaluates its result.
  1. <!DOCTYPE html>
  2. <html xmlns="http://www.w3.org/1999/xhtml">
  3. <head runat="server">
  4. </head>
  5. <body>
  6. <form id="form1" runat="server">
  7. <script>
  8. var exp = 20 + 40 - 40 + 20;
  9. var result = eval(exp);
  10. alert("Result is:- " + result);
  12. </script>
  13. </form>
  14. </body>
  15. </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.
  1. <!DOCTYPE html>
  2. <html xmlns="http://www.w3.org/1999/xhtml">
  3. <head runat="server">
  4. </head>
  5. <body>
  6. <form id="form1" runat="server">
  7. <script>
  9. var a = 20.20;
  10. var b = 200;
  11. var c = "Hello";
  12. alert("a is:- " + isNaN(a) + " b is:- " + isNaN(b) + " c is:- " + isNaN(c));
  14. </script>
  15. </form>
  16. </body>
  17. </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.
  1. <!DOCTYPE html>
  2. <html xmlns="http://www.w3.org/1999/xhtml">
  3. <head runat="server">
  4. </head>
  5. <body>
  6. <form id="form1" runat="server">
  7. <script>
  9. var a = true;
  10. var b = 200;
  11. var c = "Sagar";
  12. alert("a is:- " + Number(a) + " b is:- " + Number(b) + " c is:- " + Number(c));
  14. </script>
  15. </form>
  16. </body>
  17. </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.