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JavaScript do while loop

Description

In JavaScript do while loop executes a statement block once and then repeats the execution until a specified condition evaluates to false.

Syntax

do
{
  statement block
}
while (condition);

In while loop, the given condition is tested at the beginning, i.e. before executing any of the statements within the while loop. In case of do while loop the condition is tested after execution of the statements within the while loop. This means that do-while would execute it's statements at least once, even if the condition fails for the first time itself.

Pictorial Presentation:

javascript do while loop

Example:

The following web document calculates the sum of even numbers between 0 to 10. The do while loop starts with x = 0 and runs until it equals to 10. If the remainder of x/2 is equals to 0 we add x with y and after completion of the loop, y returns the sum of even numbers.

HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset=utf-8>
<title>JavaScript do while statement :  Example-1</title>
</head>
<body>
<h1>JavaScript : do while statement</h1>
<h3> The do while loop calculate the sum of even numbers between 0 to 10. </h3>
<p id="result">Output will be displayed here.</p>
<script src="do-while-statement-example1.js"></script>
</body>
</html>

JS Code

var x = 1;
var y = 0;
var z = 0;
document.getElementById("result").innerHTML = "List of numbers : ";
do
{
z = x %  2;
if (z === 0)
{
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode(x);
newParagraph1.appendChild(newText1);
document.body.appendChild(newParagraph1);
y=y+x;
}
x++;
}
while (x <=10 );
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode("The sum of even numbers between 0 to 10 is : " + y);
newParagraph1.appendChild(newText1);
document.body.appendChild(newParagraph1);

View the example in the browser

Practice the example online

See the Pen do-while-1 by w3resource (@w3resource) on CodePen.


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Next: JavaScript while loop

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04