How to highlight text using javascript

Can someone help me with a javascript function that can highlight text on a web page. And the requirement is to - highlight only once, not like highlight all occurrences of the text as we do in case of search.

Solution 1:

You can use the jquery highlight effect.

But if you are interested in raw javascript code, take a look at what I got Simply copy paste into an HTML, open the file and click "highlight" - this should highlight the word "fox". Performance wise I think this would do for small text and a single repetition (like you specified)

function highlight(text) {
  var inputText = document.getElementById("inputText");
  var innerHTML = inputText.innerHTML;
  var index = innerHTML.indexOf(text);
  if (index >= 0) { 
   innerHTML = innerHTML.substring(0,index) + "<span class='highlight'>" + innerHTML.substring(index,index+text.length) + "</span>" + innerHTML.substring(index + text.length);
   inputText.innerHTML = innerHTML;
  }
}

.highlight {
  background-color: yellow;
}

<button onclick="highlight('fox')">Highlight</button>

<div id="inputText">
  The fox went over the fence
</div>

Edits:

Using `replace`

I see this answer gained some popularity, I thought I might add on it. You can also easily use replace

"the fox jumped over the fence".replace(/fox/,"<span>fox</span>");

Or for multiple occurrences (not relevant for the question, but was asked in comments) you simply add global on the replace regular expression.

"the fox jumped over the other fox".replace(/fox/g,"<span>fox</span>");

Hope this helps to the intrigued commenters.

Replacing the HTML to the entire web-page

to replace the HTML for an entire web-page, you should refer to innerHTML of the document's body.

document.body.innerHTML

Solution 2:

The solutions offered here are quite bad.

You can't use regex, because that way, you search/highlight in the html tags.
You can't use regex, because it doesn't work properly with UTF* (anything with non-latin/English characters).
You can't just do an innerHTML.replace, because this doesn't work when the characters have a special HTML notation, e.g. & for &, < for <, > for >, ä for ä, ö for ö ü for ü ß for ß, etc.

What you need to do:

Loop through the HTML document, find all text nodes, get the textContent, get the position of the highlight-text with indexOf (with an optional toLowerCase if it should be case-insensitive), append everything before indexof as textNode, append the matched Text with a highlight span, and repeat for the rest of the textnode (the highlight string might occur multiple times in the textContent string).

Here is the code for this:

var InstantSearch = {

    "highlight": function (container, highlightText)
    {
        var internalHighlighter = function (options)
        {

            var id = {
                container: "container",
                tokens: "tokens",
                all: "all",
                token: "token",
                className: "className",
                sensitiveSearch: "sensitiveSearch"
            },
            tokens = options[id.tokens],
            allClassName = options[id.all][id.className],
            allSensitiveSearch = options[id.all][id.sensitiveSearch];


            function checkAndReplace(node, tokenArr, classNameAll, sensitiveSearchAll)
            {
                var nodeVal = node.nodeValue, parentNode = node.parentNode,
                    i, j, curToken, myToken, myClassName, mySensitiveSearch,
                    finalClassName, finalSensitiveSearch,
                    foundIndex, begin, matched, end,
                    textNode, span, isFirst;

                for (i = 0, j = tokenArr.length; i < j; i++)
                {
                    curToken = tokenArr[i];
                    myToken = curToken[id.token];
                    myClassName = curToken[id.className];
                    mySensitiveSearch = curToken[id.sensitiveSearch];

                    finalClassName = (classNameAll ? myClassName + " " + classNameAll : myClassName);

                    finalSensitiveSearch = (typeof sensitiveSearchAll !== "undefined" ? sensitiveSearchAll : mySensitiveSearch);

                    isFirst = true;
                    while (true)
                    {
                        if (finalSensitiveSearch)
                            foundIndex = nodeVal.indexOf(myToken);
                        else
                            foundIndex = nodeVal.toLowerCase().indexOf(myToken.toLowerCase());

                        if (foundIndex < 0)
                        {
                            if (isFirst)
                                break;

                            if (nodeVal)
                            {
                                textNode = document.createTextNode(nodeVal);
                                parentNode.insertBefore(textNode, node);
                            } // End if (nodeVal)

                            parentNode.removeChild(node);
                            break;
                        } // End if (foundIndex < 0)

                        isFirst = false;


                        begin = nodeVal.substring(0, foundIndex);
                        matched = nodeVal.substr(foundIndex, myToken.length);

                        if (begin)
                        {
                            textNode = document.createTextNode(begin);
                            parentNode.insertBefore(textNode, node);
                        } // End if (begin)

                        span = document.createElement("span");
                        span.className += finalClassName;
                        span.appendChild(document.createTextNode(matched));
                        parentNode.insertBefore(span, node);

                        nodeVal = nodeVal.substring(foundIndex + myToken.length);
                    } // Whend

                } // Next i 
            }; // End Function checkAndReplace 

            function iterator(p)
            {
                if (p === null) return;

                var children = Array.prototype.slice.call(p.childNodes), i, cur;

                if (children.length)
                {
                    for (i = 0; i < children.length; i++)
                    {
                        cur = children[i];
                        if (cur.nodeType === 3)
                        {
                            checkAndReplace(cur, tokens, allClassName, allSensitiveSearch);
                        }
                        else if (cur.nodeType === 1)
                        {
                            iterator(cur);
                        }
                    }
                }
            }; // End Function iterator

            iterator(options[id.container]);
        } // End Function highlighter
        ;


        internalHighlighter(
            {
                container: container
                , all:
                    {
                        className: "highlighter"
                    }
                , tokens: [
                    {
                        token: highlightText
                        , className: "highlight"
                        , sensitiveSearch: false
                    }
                ]
            }
        ); // End Call internalHighlighter 

    } // End Function highlight

};

Then you can use it like this:

function TestTextHighlighting(highlightText)
{
    var container = document.getElementById("testDocument");
    InstantSearch.highlight(container, highlightText);
}

Here's an example HTML document

<!DOCTYPE html>
<html>
    <head>
        <title>Example of Text Highlight</title>
        <style type="text/css" media="screen">
            .highlight{ background: #D3E18A;}
            .light{ background-color: yellow;}
        </style>
    </head>
    <body>
        <div id="testDocument">
            This is a test
            <span> This is another test</span>
            äöüÄÖÜäöüÄÖÜ
            <span>Test123&auml;&ouml;&uuml;&Auml;&Ouml;&Uuml;</span>
        </div>
    </body>
</html>

By the way, if you search in a database with LIKE,
e.g. WHERE textField LIKE CONCAT('%', @query, '%') [which you shouldn't do, you should use fulltext-search or Lucene], then you can escape every character with \ and add an SQL-escape-statement, that way you'll find special characters that are LIKE-expressions.

e.g.

WHERE textField LIKE CONCAT('%', @query, '%') ESCAPE '\'

and the value of @query is not '%completed%' but '%\c\o\m\p\l\e\t\e\d%'

(tested, works with SQL-Server and PostgreSQL, and every other RDBMS system that supports ESCAPE)

A revised typescript-version:

namespace SearchTools 
{


    export interface IToken
    {
        token: string;
        className: string;
        sensitiveSearch: boolean;
    }


    export class InstantSearch 
    {

        protected m_container: Node;
        protected m_defaultClassName: string;
        protected m_defaultCaseSensitivity: boolean;
        protected m_highlightTokens: IToken[];


        constructor(container: Node, tokens: IToken[], defaultClassName?: string, defaultCaseSensitivity?: boolean)
        {
            this.iterator = this.iterator.bind(this);
            this.checkAndReplace = this.checkAndReplace.bind(this);
            this.highlight = this.highlight.bind(this);
            this.highlightNode = this.highlightNode.bind(this);    

            this.m_container = container;
            this.m_defaultClassName = defaultClassName || "highlight";
            this.m_defaultCaseSensitivity = defaultCaseSensitivity || false;
            this.m_highlightTokens = tokens || [{
                token: "test",
                className: this.m_defaultClassName,
                sensitiveSearch: this.m_defaultCaseSensitivity
            }];
        }


        protected checkAndReplace(node: Node)
        {
            let nodeVal: string = node.nodeValue;
            let parentNode: Node = node.parentNode;
            let textNode: Text = null;

            for (let i = 0, j = this.m_highlightTokens.length; i < j; i++)
            {
                let curToken: IToken = this.m_highlightTokens[i];
                let textToHighlight: string = curToken.token;
                let highlightClassName: string = curToken.className || this.m_defaultClassName;
                let caseSensitive: boolean = curToken.sensitiveSearch || this.m_defaultCaseSensitivity;

                let isFirst: boolean = true;
                while (true)
                {
                    let foundIndex: number = caseSensitive ?
                        nodeVal.indexOf(textToHighlight)
                        : nodeVal.toLowerCase().indexOf(textToHighlight.toLowerCase());

                    if (foundIndex < 0)
                    {
                        if (isFirst)
                            break;

                        if (nodeVal)
                        {
                            textNode = document.createTextNode(nodeVal);
                            parentNode.insertBefore(textNode, node);
                        } // End if (nodeVal)

                        parentNode.removeChild(node);
                        break;
                    } // End if (foundIndex < 0)

                    isFirst = false;


                    let begin: string = nodeVal.substring(0, foundIndex);
                    let matched: string = nodeVal.substr(foundIndex, textToHighlight.length);

                    if (begin)
                    {
                        textNode = document.createTextNode(begin);
                        parentNode.insertBefore(textNode, node);
                    } // End if (begin)

                    let span: HTMLSpanElement = document.createElement("span");

                    if (!span.classList.contains(highlightClassName))
                        span.classList.add(highlightClassName);

                    span.appendChild(document.createTextNode(matched));
                    parentNode.insertBefore(span, node);

                    nodeVal = nodeVal.substring(foundIndex + textToHighlight.length);
                } // Whend

            } // Next i 

        } // End Sub checkAndReplace 


        protected iterator(p: Node)
        {
            if (p == null)
                return;

            let children: Node[] = Array.prototype.slice.call(p.childNodes);

            if (children.length)
            {
                for (let i = 0; i < children.length; i++)
                {
                    let cur: Node = children[i];

                    // https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType
                    if (cur.nodeType === Node.TEXT_NODE) 
                    {
                        this.checkAndReplace(cur);
                    }
                    else if (cur.nodeType === Node.ELEMENT_NODE) 
                    {
                        this.iterator(cur);
                    }
                } // Next i 

            } // End if (children.length) 

        } // End Sub iterator


        public highlightNode(n:Node)
        {
            this.iterator(n);
        } // End Sub highlight 


        public highlight()
        {
            this.iterator(this.m_container);
        } // End Sub highlight 


    } // End Class InstantSearch 


} // End Namespace SearchTools

Usage:

let searchText = document.getElementById("txtSearchText");
let searchContainer = document.body; // document.getElementById("someTable");
let highlighter = new SearchTools.InstantSearch(searchContainer, [
    {
        token: "this is the text to highlight" // searchText.value,
        className: "highlight", // this is the individual highlight class
        sensitiveSearch: false
    }
]);


// highlighter.highlight(); // this would highlight in the entire table
// foreach tr - for each td2 
highlighter.highlightNode(td2); // this highlights in the second column of table

How to highlight text using javascript

Solution 1:

Using `replace`

Replacing the HTML to the entire web-page

Solution 2:

Related

Recent Posts

How to highlight text using javascript

Solution 1:

Using replace

Replacing the HTML to the entire web-page

Solution 2:

Related

Recent Posts

Using `replace`