Posted By:
27 Aug, 2014 7:35 pm PDT

Switch statement in Javascript

I have heard that we can use switch statement as an alternative to if else statements.

Pease tell me how do we use it?

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You can use multiple if...else if statements, as in the previous chapter, to perform a multiway branch. However, this is not always the best solution, especially when all of the branches depend on the value of a single variable.

Starting with JavaScript 1.2, you can use a switch statement which handles exactly this situation, and it does so more efficiently than repeated if...else if statements.

Syntax:

The basic syntax of the switch statement is to give an expression to evaluate and several different statements to execute based on the value of the expression. The interpreter checks each case against the value of the expression until a match is found. If nothing matches, adefault condition will be used.

switch (expression)

{

  case condition 1: statement(s)

                    break;

  case condition 2: statement(s)

                    break;

   ...

  case condition n: statement(s)

                    break;

  default: statement(s)

}

 

The break statements indicate to the interpreter the end of that particular case. If they were omitted, the interpreter would continue executing each statement in each of the following cases.

We will explain break statement in Loop Control chapter.

Example:

Following example illustrates a basic while loop:

<script type="text/javascript">

<!--

var grade='A';

  1. ("Entering switch block<br />");

switch (grade)

{

  case 'A': document.write("Good job<br />");

            break;

  case 'B': document.write("Pretty good<br />");

            break;

  case 'C': document.write("Passed<br />");

            break;

  case 'D': document.write("Not so good<br />");

            break;

  case 'F': document.write("Failed<br />");

            break;

  default:  document.write("Unknown grade<br />")

}

  1. ("Exiting switch block");

//-->

</script>

 
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