The purpose of a while loop is to execute a statement or code block repeatedly as long as an expression is true. Share. Try the following example to implement while loop. Last modified: Feb 19, 2021, by MDN contributors. JavaScript supports different kinds of loops: for - loops through a block of code a number of times; for/in - loops through the properties of an object; for/of - loops through the values of an iterable object; while - loops through a block of code while a specified condition is true JavaScript mainly provides three ways for executing the loops. The while loop in Javascript, like in many other languages, has this structure: while (condition) { statement } The loop keeps iterating while a condition is true and the statement inside the loop is executed every time the loop runs. Use //# instead, Warning: String.x is deprecated; use String.prototype.x instead, Warning: Date.prototype.toLocaleFormat is deprecated. Therefore, x and n take on the following values: After completing the third pass, the condition n < 3 is no longer true, In this JavaScript while Loop example, First, the value inside the number variable (6) is tested against the while condition. operator, SyntaxError: missing ) after argument list, RangeError: repeat count must be non-negative, TypeError: can't delete non-configurable array element, RangeError: argument is not a valid code point, Error: Permission denied to access property "x", SyntaxError: redeclaration of formal parameter "x", TypeError: Reduce of empty array with no initial value, SyntaxError: "x" is a reserved identifier, RangeError: repeat count must be less than infinity, Warning: unreachable code after return statement, SyntaxError: "use strict" not allowed in function with non-simple parameters, ReferenceError: assignment to undeclared variable "x", ReferenceError: reference to undefined property "x", SyntaxError: function statement requires a name, TypeError: variable "x" redeclares argument, Enumerability and ownership of properties. JavaScript supports all the necessary loops to ease down the pressure of programming. The continue statement skips the rest of the code to the end of the innermost body of a loop and evaluates the expression that controls the loop. While writing a program, you may encounter a situation where you need to perform an action over and over again. JavaScript includes while loop to execute code repeatedly till it satisfies a specified condition. Follow edited Aug 25 '19 at 0:58. Instead, they rely on a condition being met to stop execution. To execute multiple statements within the loop, use a block statement ({ ... }) to group those statements. If the condition results true, the number added to the total. Here is an example of Do While loop in JavaScript. while (condition) { // execute code as long as condition is true } Here are some examples of definite loops in JavaScript: while loops let x = 0 while(x  5){ console.log(x) x++} //logs 1,2,3,4. The while loop and the do/while are explained in the next chapters. The while loop in JavaScript works exactly in the same as the while loop works in other programming languages such as C, Java, C#, etc. The condition is evaluated again. Introduction to the JavaScript while loop statement. How to break from a (for, while) Loop in JavaScript. Syntax: while (condition) { // Statements } Example: This example illustrates the use of while loop. If you have read the previous chapter, about the for loop, you will discover that a while loop is much the same as a for loop, with statement 1 and statement 3 omitted. The do...while loop is similar to the while loop except that the condition check happens at the end of the loop. In such situations, you would need to write loop statements to reduce the number of lines. This is the basic difference between do while loop and while loop. Browse other questions tagged javascript while-loop or ask your own question. The most basic types of loops used in JavaScript are the while and do...while statements, which you can review in “How To Construct While and Do…While Loops in JavaScript.” Because while and do...while statements are conditionally based, they execute when a given statement returns as evaluating to true. The while Loop. The while loop can be thought of as a repeating if statement. Each iteration, the loop increments n and adds it to x. Unlike for loop, while loop only requires condition expression. Viewed 19k times 3. The syntax is very similar to an if statement, as seen below. Improve this question. 3. The JavaScript while loop iterates the elements for the infinite number of times. Use Notepad++ to write JavaScript code that contains a While Loop, and test the code in Chrome. In JavaScript, the break statement is used to stop/ terminates the loop … Using unlabeled JavaScript continue statement. The while statement creates a loop that executes a specified statement The “while loop” is executed as long as the specified condition is true. https://github.com/mdn/interactive-examples, Warning: -file- is being assigned a //# sourceMappingURL, but already has one, TypeError: invalid Array.prototype.sort argument, Warning: 08/09 is not a legal ECMA-262 octal constant, SyntaxError: invalid regular expression flag "x", TypeError: X.prototype.y called on incompatible type, ReferenceError: can't access lexical declaration`X' before initialization, TypeError: can't access property "x" of "y", TypeError: can't assign to property "x" on "y": not an object, TypeError: can't define property "x": "obj" is not extensible, TypeError: property "x" is non-configurable and can't be deleted, TypeError: can't redefine non-configurable property "x", SyntaxError: applying the 'delete' operator to an unqualified name is deprecated, ReferenceError: deprecated caller or arguments usage, Warning: expression closures are deprecated, SyntaxError: "0"-prefixed octal literals and octal escape seq. While all the ways provide similar basic functionality, they differ in their syntax and condition checking time. JavaScript Loops while loop. The “While” loop, loops through a block of code as long as a specified condition is true. If the condition is true, the loop will be executed again. SyntaxError: test for equality (==) mistyped as assignment (=)? 2. JavaScript offers several options to repeatedly run a block of code, including while, do while, for and for-in. do statement while (condition); statement A statement that is executed at least once and is re-executed each time the condition evaluates to true. © 2005-2021 Mozilla and individual contributors. The JavaScript while statement creates a loop that executes a block of code as long as the test condition evaluates to true. Once the expression becomes false, the loop terminates. as follows: The While loop first check the condition If the given condition is true, then the statement block within the while loop … The syntax of the while loop is: while (condition) { // body of loop } Here, A while loop evaluates the condition inside the parenthesis (). Note − Don’t miss the semicolon used at the end of the do...while loop. JavaScript while Loop. The purpose of a while loop is to execute a statement or code block repeatedly as long as an expression is true. While Loops. Inside the while loop, you should include the statement that will end the loop at some point of time. Javascript while loop with if statements [closed] Ask Question Asked 7 years, 9 months ago. The JavaScript code that we are going to use is as follows. JavaScript - Loop Control - JavaScript provides full control to handle loops and switch statements. 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