Tutorials References Exercises Videos Menu
Free Website Get Certified Pro


JS Reference

JS by Category JS by Alphabet

JavaScript

JS Array JS Boolean JS Classes JS Date JS Error JS Global JS JSON JS Math JS Number JS Object JS Operators JS RegExp JS Statements JS String JS TypedArray

Window

Window Object Window Console Window History Window Location Window Navigator Window Screen

HTML DOM

HTML Documents HTML Elements HTML Attributes HTML Events HTML Event Objects HTML Collection HTML NodeList HTML DOMTokenList HTML Styles
alignContent alignItems alignSelf animation animationDelay animationDirection animationDuration animationFillMode animationIterationCount animationName animationTimingFunction animationPlayState background backgroundAttachment backgroundColor backgroundImage backgroundPosition backgroundRepeat backgroundClip backgroundOrigin backgroundSize backfaceVisibility border borderBottom borderBottomColor borderBottomLeftRadius borderBottomRightRadius borderBottomStyle borderBottomWidth borderCollapse borderColor borderImage borderImageOutset borderImageRepeat borderImageSlice borderImageSource borderImageWidth borderLeft borderLeftColor borderLeftStyle borderLeftWidth borderRadius borderRight borderRightColor borderRightStyle borderRightWidth borderSpacing borderStyle borderTop borderTopColor borderTopLeftRadius borderTopRightRadius borderTopStyle borderTopWidth borderWidth bottom boxShadow boxSizing captionSide caretColor clear clip color columnCount columnFill columnGap columnRule columnRuleColor columnRuleStyle columnRuleWidth columns columnSpan columnWidth counterIncrement counterReset cssFloat cursor direction display emptyCells filter flex flexBasis flexDirection flexFlow flexGrow flexShrink flexWrap font fontFamily fontSize fontStyle fontVariant fontWeight fontSizeAdjust height isolation justifyContent left letterSpacing lineHeight listStyle listStyleImage listStylePosition listStyleType margin marginBottom marginLeft marginRight marginTop maxHeight maxWidth minHeight minWidth objectFit objectPosition opacity order orphans outline outlineColor outlineOffset outlineStyle outlineWidth overflow overflowX overflowY padding paddingBottom paddingLeft paddingRight paddingTop pageBreakAfter pageBreakBefore pageBreakInside perspective perspectiveOrigin position quotes resize right scrollBehavior tableLayout tabSize textAlign textAlignLast textDecoration textDecorationColor textDecorationLine textDecorationStyle textIndent textOverflow textShadow textTransform top transform transformOrigin transformStyle transition transitionProperty transitionDuration transitionTimingFunction transitionDelay unicodeBidi userSelect verticalAlign visibility width wordBreak wordSpacing wordWrap widows zIndex

Web APIs

API Console API Fetch API Fullscreen API Geolocation API History API MediaQueryList API Storage API Validation API Web

HTML Objects

<a> <abbr> <address> <area> <article> <aside> <audio> <b> <base> <bdo> <blockquote> <body> <br> <button> <canvas> <caption> <cite> <code> <col> <colgroup> <datalist> <dd> <del> <details> <dfn> <dialog> <div> <dl> <dt> <em> <embed> <fieldset> <figcaption> <figure> <footer> <form> <head> <header> <h1> - <h6> <hr> <html> <i> <iframe> <img> <ins> <input> button <input> checkbox <input> color <input> date <input> datetime <input> datetime-local <input> email <input> file <input> hidden <input> image <input> month <input> number <input> password <input> radio <input> range <input> reset <input> search <input> submit <input> text <input> time <input> url <input> week <kbd> <label> <legend> <li> <link> <map> <mark> <menu> <menuitem> <meta> <meter> <nav> <object> <ol> <optgroup> <option> <output> <p> <param> <pre> <progress> <q> <s> <samp> <script> <section> <select> <small> <source> <span> <strong> <style> <sub> <summary> <sup> <table> <tbody> <td> <tfoot> <th> <thead> <tr> <textarea> <time> <title> <track> <u> <ul> <var> <video>

Other References

CSSStyleDeclaration JS Conversion


JavaScript while Loop

Example

Loop a code block as long as a i is less than 5:

let text = "";
let i = 0;
while (i < 5) {
  text += i + "<br>";
  i++;
}
Try it Yourself »

Loop (iterate over) an array to collect car names:

const cars = ["BMW", "Volvo", "Saab", "Ford"];
let text = "";
let i = 0;
while (i < cars.length) {
  text += cars[i] + "<br>";
  i++;
}
Try it Yourself »
  • The loop starts in position 0 (let i = 0).
  • The loop increments i for each run (i++).
  • The loop runs as long as i < cars.length.

More examples below.


Definition and Usage

The while statement creates a loop (araund a code block) that is executed while a condition is true.

The loop runs while the condition is true. Otherwise it stops.


JavaScript Loop Statements

StatementDescription
breakBreaks out of a loop
continueSkips a value in a loop
whileLoops a code block while a condition is true
do...whileLoops a code block once, and then while a condition is true
forLoops a code block while a condition is true
for...ofLoops the values of any iterable
for...inLoops the properties of an object

Syntax

while (condition) {
  code block to be executed
}

Parameters

Parameter Description
condition Required.
The condition for running the code block. If it returns true, the code clock will start over again, otherwise it ends.

Note

If the condition is always true, the loop will never end. This will crash your browser.

If you use a variable in the condition, you must initialize it before the loop, and increment it within the loop. Otherwise the loop will never end. This will also crash your browser.



More Examples

Loop over an array in descending order (negative increment):

const cars = ["BMW", "Volvo", "Saab", "Ford"];
let text = "";
let len = cars.length;
while (len--) {
  text += cars[len] + "<br>";
}
Try it Yourself »

Using break - Loop through a block of code, but exit the loop when i == 3:

let text = "";
let i = 0;
while (i < 5) {
  text += i + "<br>";
  i++;
  if (i == 3) break;
}
Try it Yourself »

Using continue - Loop through a block of code, but skip the value 3:

let text = "";
let i = 0;
while (i < 5) {
  i++;
  if (i == 3) continue;
  text += i + "<br>";
}
Try it Yourself »

Browser Support

while is an ECMAScript1 (ES1) feature.

ES1 (JavaScript 1997) is fully supported in all browsers:

Chrome IE Edge Firefox Safari Opera
Yes Yes Yes Yes Yes Yes