JavaScript Do While
JavaScript do...while loop check condition and execute a block of code for a specify number of times, until the condition become false.
JavaScript do...while block of statements executed before evaluated the condition. At least one time block of statements executes if the condition doesn't satisfy.
JavaScript Do While Loop
Syntax
do {
statements; // Do stuff if while true
increment; // Update condition variable value
} while (condition)
do {
...
...
} while (true) // condition evaluates to true
do {
...
...
} while (1) // Condition always true
Example: Following do...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 do...while block.
<script>
number = 1;
do {
document.writeln(number + " times");
number++;
} while (number <= 10)
document.writeln("Total " + (number - 1) + " times loop repeat");
</script>
Example Result
Array Loops in JavaScript
do...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;
do {
document.writeln("Value of arr[" + number + "] : " + arr[number]);
number++;
} while (number < arr.length)
document.writeln("End of Loop.");
</script>
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 - 1; // array index start from 0
do{
document.writeln("Value of arr[" + number + "] : " + arr[number]);
} while (number--)
document.writeln("End of Loop.");
</script>
Example Result