Parse an HTML string with JS

322

votes

I searched for a solution but nothing was relevant, so here is my problem:

I want to parse a string which contains HTML text. I want to do it in JavaScript.

I tried this library but it seems that it parses the HTML of my current page, not from a string. Because when I try the code below, it changes the title of my page:

var parser = new HTMLtoDOM("<html><head><title>titleTest</title></head><body><a href='test0'>test01</a><a href='test1'>test02</a><a href='test2'>test03</a></body></html>", document);

My goal is to extract links from an HTML external page that I read just like a string.

Do you know an API to do it?

javascripthtmldomhtml-parsing

possible duplicate of JavaScript DOMParser access innerHTML and other properties - Rob W

The method on the linked duplicate creates a HTML document from a given string. Then, you can use doc.getElementsByTagName('a') to read the links (or even doc.links). - Rob W

It's worth mentioning that if you're using a framework like React.js then there may be ways of doing it that are specific to the framework such as: stackoverflow.com/questions/23616226/… - Mike Lyons

Does this answer your question? Strip HTML from Text JavaScript - Leif Arne Storset

442

votes

Create a dummy DOM element and add the string to it. Then, you can manipulate it like any DOM element.

var el = document.createElement( 'html' );
el.innerHTML = "<html><head><title>titleTest</title></head><body><a href='test0'>test01</a><a href='test1'>test02</a><a href='test2'>test03</a></body></html>";

el.getElementsByTagName( 'a' ); // Live NodeList of your anchor elements

Edit: adding a jQuery answer to please the fans!

var el = $( '<div></div>' );
el.html("<html><head><title>titleTest</title></head><body><a href='test0'>test01</a><a href='test1'>test02</a><a href='test2'>test03</a></body></html>");

$('a', el) // All the anchor elements

299

votes

It's quite simple:

var parser = new DOMParser();
var htmlDoc = parser.parseFromString(txt, 'text/html');
// do whatever you want with htmlDoc.getElementsByTagName('a');

According to MDN, to do this in chrome you need to parse as XML like so:

var parser = new DOMParser();
var htmlDoc = parser.parseFromString(txt, 'text/xml');
// do whatever you want with htmlDoc.getElementsByTagName('a');

~~It is currently unsupported by webkit and you'd have to follow Florian's answer, and it is unknown to work in most cases on mobile browsers.~~

Edit: Now widely supported

27

votes

EDIT: The solution below is only for HTML "fragments" since html,head and body are removed. I guess the solution for this question is DOMParser's parseFromString() method:

const parser = new DOMParser();
const document = parser.parseFromString(html, "text/html");

For HTML fragments, the solutions listed here works for most HTML, however for certain cases it won't work.

For example try parsing <td>Test</td>. This one won't work on the div.innerHTML solution nor DOMParser.prototype.parseFromString nor range.createContextualFragment solution. The td tag goes missing and only the text remains.

Only jQuery handles that case well.

So the future solution (MS Edge 13+) is to use template tag:

function parseHTML(html) {
    var t = document.createElement('template');
    t.innerHTML = html;
    return t.content;
}

var documentFragment = parseHTML('<td>Test</td>');

For older browsers I have extracted jQuery's parseHTML() method into an independent gist - https://gist.github.com/Munawwar/6e6362dbdf77c7865a99

21

votes

var doc = new DOMParser().parseFromString(html, "text/html");
var links = doc.querySelectorAll("a");

7

votes

The following function parseHTML will return either :

a Document when your file starts with a doctype.
a DocumentFragment when your file doesn't start with a doctype.

The code :

function parseHTML(markup) {
    if (markup.toLowerCase().trim().indexOf('<!doctype') === 0) {
        var doc = document.implementation.createHTMLDocument("");
        doc.documentElement.innerHTML = markup;
        return doc;
    } else if ('content' in document.createElement('template')) {
       // Template tag exists!
       var el = document.createElement('template');
       el.innerHTML = markup;
       return el.content;
    } else {
       // Template tag doesn't exist!
       var docfrag = document.createDocumentFragment();
       var el = document.createElement('body');
       el.innerHTML = markup;
       for (i = 0; 0 < el.childNodes.length;) {
           docfrag.appendChild(el.childNodes[i]);
       }
       return docfrag;
    }
}

How to use :

var links = parseHTML('<!doctype html><html><head></head><body><a>Link 1</a><a>Link 2</a></body></html>').getElementsByTagName('a');

6

votes

The fastest way to parse HTML in Chrome and Firefox is Range#createContextualFragment:

var range = document.createRange();
range.selectNode(document.body); // required in Safari
var fragment = range.createContextualFragment('<h1>html...</h1>');
var firstNode = fragment.firstChild;

I would recommend to create a helper function which uses createContextualFragment if available and falls back to innerHTML otherwise.

Benchmark: http://jsperf.com/domparser-vs-createelement-innerhtml/3

5

votes

If you're open to using jQuery, it has some nice facilities for creating detached DOM elements from strings of HTML. These can then be queried through the usual means, E.g.:

var html = "<html><head><title>titleTest</title></head><body><a href='test0'>test01</a><a href='test1'>test02</a><a href='test2'>test03</a></body></html>";
var anchors = $('<div/>').append(html).find('a').get();

Edit - just saw @Florian's answer which is correct. This is basically exactly what he said, but with jQuery.

5

votes

const parse = Range.prototype.createContextualFragment.bind(document.createRange());

document.body.appendChild( parse('<p><strong>Today is:</strong></p>') ),
document.body.appendChild( parse(`<p style="background: #eee">${new Date()}</p>`) );

NodeNodeRange

// <body> is "parent" Node, start of Range
const parseRange = document.createRange();
const parse = Range.prototype.createContextualFragment.bind(parseRange);

// Returns Text "1 2" because td, tr, tbody are not valid children of <body>
parse('<td>1</td> <td>2</td>');
parse('<tr><td>1</td> <td>2</td></tr>');
parse('<tbody><tr><td>1</td> <td>2</td></tr></tbody>');

// Returns <table>, which is a valid child of <body>
parse('<table> <td>1</td> <td>2</td> </table>');
parse('<table> <tr> <td>1</td> <td>2</td> </tr> </table>');
parse('<table> <tbody> <td>1</td> <td>2</td> </tbody> </table>');

// <tr> is parent Node, start of Range
parseRange.setStart(document.createElement('tr'), 0);

// Returns [<td>, <td>] element array
parse('<td>1</td> <td>2</td>');
parse('<tr> <td>1</td> <td>2</td> </tr>');
parse('<tbody> <td>1</td> <td>2</td> </tbody>');
parse('<table> <td>1</td> <td>2</td> </table>');

2

votes

1 Way

Use document.cloneNode()

Performance is:

Call to document.cloneNode() took ~0.22499999977299012 milliseconds.

and maybe will be more.

var t0, t1, html;

t0 = performance.now();
   html = document.cloneNode(true);
t1 = performance.now();

console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")

html.documentElement.innerHTML = '<!DOCTYPE html><html><head><title>Test</title></head><body><div id="test1">test1</div></body></html>';

console.log(html.getElementById("test1"));

2 Way

Use document.implementation.createHTMLDocument()

Performance is:

Call to document.implementation.createHTMLDocument() took ~0.14000000010128133 milliseconds.

var t0, t1, html;

t0 = performance.now();
html = document.implementation.createHTMLDocument("test");
t1 = performance.now();

console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")

html.documentElement.innerHTML = '<!DOCTYPE html><html><head><title>Test</title></head><body><div id="test1">test1</div></body></html>';

console.log(html.getElementById("test1"));

3 Way

Use document.implementation.createDocument()

Performance is:

Call to document.implementation.createHTMLDocument() took ~0.14000000010128133 milliseconds.

var t0 = performance.now();
  html = document.implementation.createDocument('', 'html', 
             document.implementation.createDocumentType('html', '', '')
         );
var t1 = performance.now();

console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")

html.documentElement.innerHTML = '<html><head><title>Test</title></head><body><div id="test1">test</div></body></html>';

console.log(html.getElementById("test1"));

4 Way

Use new Document()

Performance is:

Call to document.implementation.createHTMLDocument() took ~0.13499999840860255 milliseconds.

Note

ParentNode.append is experimental technology in 2020 year.

var t0, t1, html;

t0 = performance.now();
//---------------
html = new Document();

html.append(
  html.implementation.createDocumentType('html', '', '')
);
    
html.append(
  html.createElement('html')
);
//---------------
t1 = performance.now();

console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")

html.documentElement.innerHTML = '<html><head><title>Test</title></head><body><div id="test1">test1</div></body></html>';

console.log(html.getElementById("test1"));

0

votes

for me. i had to use innerhtml of an element parsed in popover of angular ngx bootstrap popover this is the solution which worked for me

public htmlContainer = document.createElement( 'html' );

in constructor

this.htmlContainer.innerHTML = ''; setTimeout(() => { this.convertToArray(); });

 convertToArray() {
    const shapesHC = document.getElementsByClassName('weekPopUpDummy');
    const shapesArrHCSpread = [...(shapesHC as any)];
    this.htmlContainer = shapesArrHCSpread[0];
    this.htmlContainer.innerHTML = shapesArrHCSpread[0].textContent;
  }

in html

<div class="weekPopUpDummy" [popover]="htmlContainer.innerHTML" [adaptivePosition]="false" placement="top" [outsideClick]="true" #popOverHide="bs-popover" [delay]="150" (onHidden)="onHidden(weekEvent)" (onShown)="onShown()">

-1

votes

let content = "<center><h1>404 Not Found</h1></center>"
let result = $("<div/>").html(content).text()

content: <center><h1>404 Not Found</h1></center>,
result: "404 Not Found"

Parse an HTML string with JS

11 Answers

The code :

How to use :