Connor Mills

Connor Mills

1552016988

Is there a JavaScript / jQuery DOM change listener?

Essentially I want to have a script execute when the contents of a DIV change. Since the scripts are separate (content script in the Chrome extension & webpage script), I need a way simply observe changes in DOM state. I could set up polling but that seems sloppy.

#javascript #jquery #google-chrome

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Riley Lambert

1552019944

Several years later, there is now officially a better solution. DOM4 Mutation Observers are the replacement for deprecated DOM3 mutation events. They are currently implemented in modern browsers as MutationObserver (or as the vendor-prefixed WebKitMutationObserver in old versions of Chrome):

MutationObserver = window.MutationObserver || window.WebKitMutationObserver;

var observer = new MutationObserver(function(mutations, observer) {
    // fired when a mutation occurs
    console.log(mutations, observer);
    // ...
});

// define what element should be observed by the observer
// and what types of mutations trigger the callback
observer.observe(document, {
  subtree: true,
  attributes: true
  //...
});

This example listens for DOM changes on document and its entire subtree, and it will fire on changes to element attributes as well as structural changes. The draft spec has a full list of valid mutation listener properties:

childList* Set to true if mutations to target’s children are to be observed.
childList* Set to true if mutations to target’s children are to be observed.
childList* Set to true if mutations to target’s children are to be observed.
childList* Set to true if mutations to target’s children are to be observed.
childList* Set to true if mutations to target’s children are to be observed.
childList* Set to true if mutations to target’s children are to be observed.
childList* Set to true if mutations to target’s children are to be observed.

Alfie Mellor

1552020016

This answer is now deprecated. See the answer by apsillers.

Since this is for a Chrome extension, you might as well use the standard DOM event - DOMSubtreeModified. See the support for this event across browsers. It has been supported in Chrome since 1.0.

$("#someDiv").bind("DOMSubtreeModified", function() {
    alert("tree changed");
});

See a working example here.

Brooke Giles

1552020065

nother approach depending on how you are changing the div. If you are using JQuery to change a div’s contents with its html() method, you can extend that method and call a registration function each time you put html into a div.

(function( $, oldHtmlMethod ){
    // Override the core html method in the jQuery object.
    $.fn.html = function(){
        // Execute the original HTML method using the
        // augmented arguments collection.

        var results = oldHtmlMethod.apply( this, arguments );
        com.invisibility.elements.findAndRegisterElements(this);
        return results;

    };
})( jQuery, jQuery.fn.html );

We just intercept the calls to html(), call a registration function with this, which in the context refers to the target element getting new content, then we pass on the call to the original jquery.html() function. Remember to return the results of the original html() method, because JQuery expects it for method chaining.

For more info on method overriding and extension, check out http://www.bennadel.com/blog/2009-Using-Self-Executing-Function-Arguments-To-Override-Core-jQuery-Methods.htm, which is where I cribbed the closure function. Also check out the plugins tutorial at JQuery’s site

John David

1552020092

In addition to the “raw” tools provided by [MutationObserver](https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver "MutationObserver") API, there exist “convenience” libraries to work with DOM mutations.

Consider: MutationObserver represents each DOM change in terms of subtrees. So if you’re, for instance, waiting for a certain element to be inserted, it may be deep inside the children of mutations.mutation[i].addedNodes[j].

Another problem is when your own code, in reaction to mutations, changes DOM - you often want to filter it out.

A good convenience library that solves such problems is [mutation-summary](https://github.com/rafaelw/mutation-summary "mutation-summary") (disclaimer: I’m not the author, just a satisfied user), which enables you to specify queries of what you’re interested in, and get exactly that.

Basic usage example from the docs:

var observer = new MutationSummary({
  callback: updateWidgets,
  queries: [{
    element: '[data-widget]'
  }]
});

function updateWidgets(summaries) {
  var widgetSummary = summaries[0];
  widgetSummary.added.forEach(buildNewWidget);
  widgetSummary.removed.forEach(cleanupExistingWidget);
}

Dylan Iqbal

1552020129

Many sites use AJAX to add/show/change content dynamically. Sometimes it’s used instead of in-site navigation, so current URL is changed programmatically and content scripts aren’t automatically executed by browser in this case since the page isn’t fetched from remote server entirely.

Usual JS methods of detecting page changes available in a content script.

document.head.appendChild(document.createElement('script')).text = '(' +
    function() {
        // injected DOM script is not a content script anymore, 
        // it can modify objects and functions of the page
        var _pushState = history.pushState;
        history.pushState = function(state, title, url) {
            _pushState.call(this, state, title, url);
            window.dispatchEvent(new CustomEvent('state-changed', {detail: state}));
        };
        // repeat the above for replaceState too
    } + ')(); this.remove();'; // remove the DOM script element

// And here content script listens to our DOM script custom events
window.addEventListener('state-changed', function(e) {
    console.log('History state changed', e.detail, location.hash);
    doSomething();
});

window.addEventListener('hashchange', function(e) {
    console.log('URL hash changed', e);
    doSomething();
});
window.addEventListener('popstate', function(e) {
    console.log('State changed', e);
    doSomething();
});

Extensions-specific: detect URL changes in a background / event page.

There are advanced API to work with navigation: webNavigationwebRequest, but we’ll use simple chrome.tabs.onUpdated event listener that sends a message to the content script:

var rxLookfor = /^https?:\/\/(www\.)?google\.(com|\w\w(\.\w\w)?)\/.*?[?#&]q=/;
chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab) {
    if (rxLookfor.test(changeInfo.url)) {
        chrome.tabs.sendMessage(tabId, 'url-update');
    }
});

chrome.runtime.onMessage.addListener(function(msg, sender, sendResponse) {
    if (msg === 'url-update') {
        doSomething();
    }
});

Abigale  Yundt

Abigale Yundt

1602841440

JavaScript vs jQuery — Learn DOM manipulation without using jQuery

jQuery has been the savior for so many new and coming Web Developers, including myself. If you wanted to learn Web Development back in the day, learning jQuery was an absolute given. This was mainly because jQuery took much of the cross-browser compatibility issues out and enabled developers to write code without having to worry about whether the features that they are implementing will work on all browsers.

But with improvements in browser standards and most of jQuery’s API’s integrated into JavaScript, jQuery has become a little redundant. Moreover, with native browser API’s it is so much easier to debug code, and being native, most of these API’s offer better performance than jQuery’s API’s. Besides, you will have one less library to add to your script imports. If you’re still not sold on parting with jQuery maybe this answer will help.

So, if you’re considering a move away from jQuery, I have compiled a list of common jQuery methods and API’s that people use, with their Vanilla JS alternatives (Vanilla JS is a fancy name for plain JavaScript code without the use of any libraries). Let’s dive in!

Querying the DOM

The bread and butter of jQuery is it’s amazing ability to query DOM elements. This is demonstrated below:

jQuery('div.home')

However, you can achieve the same thing with JavaScript using it **document.querySelector() **and document.querySelectorAll() methods. Below is their implementation.

#javascript #replace-jquery #jquery #jquery-vs-javascript #faisal-rashid

Connor Mills

Connor Mills

1552016988

Is there a JavaScript / jQuery DOM change listener?

Essentially I want to have a script execute when the contents of a DIV change. Since the scripts are separate (content script in the Chrome extension & webpage script), I need a way simply observe changes in DOM state. I could set up polling but that seems sloppy.

#javascript #jquery #google-chrome

Rahul Jangid

1622207074

What is JavaScript - Stackfindover - Blog

Who invented JavaScript, how it works, as we have given information about Programming language in our previous article ( What is PHP ), but today we will talk about what is JavaScript, why JavaScript is used The Answers to all such questions and much other information about JavaScript, you are going to get here today. Hope this information will work for you.

Who invented JavaScript?

JavaScript language was invented by Brendan Eich in 1995. JavaScript is inspired by Java Programming Language. The first name of JavaScript was Mocha which was named by Marc Andreessen, Marc Andreessen is the founder of Netscape and in the same year Mocha was renamed LiveScript, and later in December 1995, it was renamed JavaScript which is still in trend.

What is JavaScript?

JavaScript is a client-side scripting language used with HTML (Hypertext Markup Language). JavaScript is an Interpreted / Oriented language called JS in programming language JavaScript code can be run on any normal web browser. To run the code of JavaScript, we have to enable JavaScript of Web Browser. But some web browsers already have JavaScript enabled.

Today almost all websites are using it as web technology, mind is that there is maximum scope in JavaScript in the coming time, so if you want to become a programmer, then you can be very beneficial to learn JavaScript.

JavaScript Hello World Program

In JavaScript, ‘document.write‘ is used to represent a string on a browser.

<script type="text/javascript">
	document.write("Hello World!");
</script>

How to comment JavaScript code?

  • For single line comment in JavaScript we have to use // (double slashes)
  • For multiple line comments we have to use / * – – * /
<script type="text/javascript">

//single line comment

/* document.write("Hello"); */

</script>

Advantages and Disadvantages of JavaScript

#javascript #javascript code #javascript hello world #what is javascript #who invented javascript

Myah  Conn

Myah Conn

1591329120

JQuery vs Vanilla JavaScript Codes, DOM and Css Selectors

jQuery vs vanilla JavaScript codes, DOM and css selectors, form validation

#javascript #jquery #dom

Hire Dedicated JavaScript Developers -Hire JavaScript Developers

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