In real-time programming, the JavaScript If Statement is one of the most valuable decision-making statements. JavaScript If Statement allows the compiler to test the condition first, depending upon the result, it will execute the statements. If the test condition is true, then only statements within the if statement executed.
JavaScript If Statement Syntax
The JavaScript If Statement has a simple structure:
if (test condition)
{
Statement 1;
Statement 2;
Statement 3;
………….
………….
Statement n;
}From the above JS code, If the test condition in the If statement is true, the statements (Statement 1, Statement 2, Statement 3, ……., Statement n) will execute. Otherwise, all these statements will skip.
JavaScript If Statement Example
This program will check for the positive number using JavaScript if statement
<!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 are not required, but for multiple or group of statements, it is mandatory. It is always good practice to use curly brackets following the JavaScript If statements.
OUTPUT
When you open the browser, below shown prompt box will be opened
We left to default 9 and Clicked OK
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 prints nothing because we don’t have anything to print after the if statement. I hope you are confused. Let us see the flow chart of If Statement for better understanding.
JavaScript If Statement Flow Chart
If the test condition is true, STATEMENT 1 execute followed by STATEMENT N. If it is False, STATEMENT N executes because it is out of the if block, and it has nothing to do with the condition result
<!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
If 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 fail the condition deliberately
If condition failed because -33 is less than 1, and it displays nothing from the JS If statement block. So, it is showing only one statement outside the statement block.
