Core JavaScript

Intermediate JavaScript

JavaScript Reference


JavaScript While Loop


JavaScript While Loop check condition and execute while block for a specify number of times, until while condition become false.

In while loop condition check first. If condition become true, execute a block of code executed.

Syntax :

while (condition) {
	statements; 	// Do stuff if while true
	increment;		// Update condition variable value
}
while (true) {		// condition evaluates to true
	...
	...
}
while (1) {			// Condition always true
	...
	...
}

Example : Following while loop example execute block of code until number value become 10. When number value become 11 the condition no longer satisfy and finally skip to execute while block.

<script>
    number = 1;
    while (number <= 10) {
        document.writeln(number + " times");
        number++;
    }
    document.writeln("Total " + (number - 1) + " times loop repeat");
</script>

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Example Result :


Array Loops in JavaScript

While loop to go through array,

JavaScript array.length property indicates length of a array.

<script>
    var arr = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
    number = 0;
    while (number < arr.length) {
        document.writeln("Value of arr[" + number + "] : " + arr[number]);
        number++;
    }
    document.writeln("End of Loop.");
</script>

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Example Result :


Reverse Array Loop in JavaScript

Following example display all array elements value in reverse order.

<script>
	var arr = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
	number = arr.length;
	while (number--) {
	    document.writeln("Value of arr[" + number + "] : " + arr[number]);
	}
    document.writeln("End of Loop.");
</script>

Run it...   »

Example Result :