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JavaScript If Statement

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The JavaScript If Statement is one of the most useful decision-making statements in real time programming. It allows the compiler to test the condition first and then, depending upon the result it will execute the statements. If the test condition is true then only statements with in the if statement is executed.

JavaScript If Statement Syntax

JavaScript If Statement has simple structure:

if (test condition)
{
 
  Statement 1;
  Statement 2;
  Statement 3;
  ………….
  ………….
  Statement n;
}

From the above code, If the test condition in the If statement is true then the statements (Statement 1, Statement 2, Statement 3, ……., Statement n) will be executed, otherwise all these statements will be skipped.

JavaScript If Statement Example

This program will check for the positive number using if statement

JAVASCRIPT CODE

<!DOCTYPE html>

<html>
<head>
    <title> JavaScript If Statement </title>
</head>
 <h1> JavaScript If Statement </h1>
<body>
<script>
  var number = prompt("Please Enter any integer Value:", "9");
  if( number >= 1 )
  {
    document.write("You Have Entered Positive Integer");
  }
</script>
</body>
</html>

NOTE: For the single statement curly brackets is not required but for multiple or group of statements it is mandatory. It is always good practice to use curly brackets following the If statements.

OUTPUT

When you open the browser, below shown prompt box will be opened
JavaScript If Statement 1

We left to default 9 and Clicked OK

JavaScript If Statement 2

If you look at the above if condition, Value stored in the number variable is greater than zero that’s why it is displaying statement inside the curly brackets ({ }).

From the above example, what happens if the condition fails? (number < 1).

It print nothing because we don’t have nothing to print after the if statement. Hope you are confused, Let us see the flow chart for better understanding.

JavaScript If Statement Flow Chart

JavaScript If Statement Flow Chart
If the test condition is true then STATEMENT 1 is executed followed by STATEMENT N. If the condition is False then STATEMENT N is executed because it is out of the if condition block and it has nothing to do with the condition result.
JAVASCRIPT CODE 

<!DOCTYPE html>

<html>
<head>
    <title> JavaScript If Statement </title>
</head>
 <h1> JavaScript If Statement </h1>
<body>
<script>
  var number = prompt("Please Enter any integer Value:", "9");
  if( number >= 1 )
  {
    document.write("You Have Entered Positive Integer:  " + number);
  }
  document.write("<br \> This Message is not coming from IF STATEMENT\n");
</script>
</body>
</html>

OUTPUT

Here also we left the number to default 9

JavaScript If Statement 3

You can observe from the above output, it is displaying both the statements because 9 is greater than 1. Let’s try the negative values to deliberately fail the condition

JavaScript If Statement 4

If condition is failed here, because -33 is less than 1. It display nothing from the If statement block so, it is displaying only one statement which is outside the statement block.

JavaScript If Statement 5

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