Tutorials References Exercises Videos Menu
Create Website Get Certified Upgrade


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 Precedence 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 Collection HTML NodeList HTML DOMTokenList HTML Styles
alignContent alignItems alignSelf animation animationDelay animationDirection animationDuration animationFillMode animationIterationCount animationName animationTimingFunction animationPlayState background backgroundAttachment backgroundClip backgroundColor backgroundImage backgroundOrigin backgroundPosition backgroundRepeat 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

HTML Events

HTML Events HTML Event Objects

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 String indexOf()

Examples

Search a string for "welcome":

let text = "Hello world, welcome to the universe.";
let result = text.indexOf("welcome");
Try it Yourself »

Search a string for "Welcome":

let text = "Hello world, welcome to the universe.";
let result = text.indexOf("Welcome");
Try it Yourself »

Find the first occurrence of "e":

let text = "Hello world, welcome to the universe.";
text.indexOf("e");
Try it Yourself »

Find the first occurrence of "e", starting at position 5:

let text = "Hello world, welcome to the universe.";
text.indexOf("e", 5);
Try it Yourself »

Find the first occurrence of "a":

let text = "Hello world, welcome to the universe.";
text.indexOf("a");
Try it Yourself »

Definition and Usage

The indexOf() method returns the position of the first occurrence of a value in a string.

The indexOf() method returns -1 if the value is not found.

The indexOf() method is case sensitive.


Syntax

string.indexOf(searchvalue, start)

Parameters

Parameter Description
searchvalue Required.
The string to search for.
start Optional.
The position to start from (default is 0).

Return Value

Type Description
A numberThe first position where the search-value occurs.
-1 if it never occurs.


The Differense Between
String indexOf() and String search()

The indexOf() method cannot search against a regular expression.

The search() cannot take a start position argument.



Browser Support

indexOf() is an ECMAScript1 (ES1) feature.

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

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