Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using this site, you agree to have read and accepted our The check && num is false when num is null or a empty string. JavaScript while loop. The JavaScript for loop is similar to the Java and C for loop. as long as a specified condition is true.In the following example, the code in the loop will run, over and over again, as long as The syntax of the while loop is: while (condition) { // body of loop } Here, A while loop evaluates the condition inside the parenthesis (). A for statement looks as follows:When a for loop executes, the following occurs: 1. If you'd like to contribute to the data, please check out Flow Chart. The condition expressio… If you'd like to contribute to the interactive examples project, please clone Get the latest and greatest from MDN delivered straight to your inbox.The newsletter is offered in English only at the moment. If the condition evaluates to true, the code inside the while loop is executed. If you haven't already, click this link to download a ZIP file containing templates for JavaScript in 60 Minutes. W3Schools is optimized for learning, testing, and training. Then the while loop stops too. Syntax This will crash your browser.Do not forget to increase the variable used in the condition, otherwise
much the same as a for loop, with statement 1 and statement 3 omitted.If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail: a variable (i) is less than 10:If you forget to increase the variable used in the condition, the loop will never end. JavaScript DO WHILE loop example. Once the expression becomes false, the loop terminates. 2. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true. This will enable you to code along. The purpose of a while loop is to execute a statement or code block repeatedly as long as an expression is true.
The loop do..while repeats while both checks are truthy: The check for num <= 100 – that is, the entered value is still not greater than 100. Sign in to enjoy the benefits of an MDN account. Then, open the while-loops.html file in Brackets. JavaScript supports different kinds of loops: The most basic loop in JavaScript is the while loop which would be discussed in this chapter. Let's create a while loop in JavaScript replicating the situation above: counting from 0 to 3. The flow chart of while loop looks as follows − Syntax Examples might be simplified to improve reading and basic understanding. Loops can execute a block of code This expression usually initializes one or more loop counters, but the syntax allows an expression of any degree of complexity. This expression can also declare variables. If you haven’t already created an account, you will be prompted to do so after signing in. var n = 0; var x = 0; while (n < 3) { n++; x += n; } Each iteration, the loop increments n and adds it to x . P.S. The initializing expression initialExpression, if any, is executed. A for loop repeats until a specified condition evaluates to false. statement creates a loop that is executed while a specified condition is true.The loop Coding a while loop. The compatibility table on this page is generated from structured data. The do/while statement is used when you want to run a loop at least one time, no matter what. The do/while statement creates a loop that executes a block of code once, before checking if the condition is true, then it will repeat the loop as long as the condition is true. i.e. The code block inside the DO statement will execute as long as the condition in the WHILE brackets equates to true. The while Loop. The source for this interactive example is stored in a GitHub repository. Therefore, x and n take on the following values: The condition is evaluated again. The Do/While Loop. The do/while loop is a variant of the while loop. This is a beginner’s tutorial on how to create a DO/WHILE loop in JavaScript. the loop will never end!If you have read the previous chapter, about the for loop, you will discover that a while loop is