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How to return a wrapper Object instead of HTML element?

I am writing a micro-library instead of using jQuery. I need only 3-4 methods ( for DOM traversal, Adding Eventlisteners etc). So I decided to write them myself instead of bloating the site with jQuery.
Here is the snippet from the code:
lib.js
window.twentyFourJS = (function() {
let elements;
const Constructor = function(selector) {
elements = document.querySelectorAll(selector);
this.elements = elements;
};
Constructor.prototype.addClass = function(className) {
elements.forEach( item => item.classList.add(className));
return this;
};
Constructor.prototype.on = function(event, callback, useCapture = false){
elements.forEach((element) => {
element.addEventListener(event, callback, useCapture);
});
return this;
}
const initFunction = function(selector){
return new Constructor(selector);
}
return initFunction;
})(twentyFourJS);
script.js
(function($){
$('.tab-menu li a').on('click', function(event) {
console.log('I am clicked'); // This works
this.addClass('MyClass'); // This does NOT work (as expected)
// I want to be able to do this
$(this).addClass('MyClass');
event.preventDefault();
});
})(twentyFourJS);
Basically I want to be able to use $(this) like we use it in jQuery.
this.addClass('MyClass') and $(this).addClass('MyClass') won't work and this is the expected behaviour.
As per my understanding this is referring to the plain HTML element. So it does not have access to any Constructor methods. it won't work.
And I have not written any code that will wrap element in Constructor object in $(this). I will have to do some changes to my Constructor so that I can access the Constructor functions using $(this). What are those changes/addition to it?
Kindly recommend only Vanilla JS ways instead of libraries.

in your constructor you need to see what you have and handle it in different ways.
const Constructor = function(selector) {
if (typeof selector === 'string') {
elements = document.querySelectorAll(selector);
} else {
// need some sort of check to see if collection or single element
// This could be improved since it could fail when someone would add a length property/attribute
elements = selector.length ? selector : [selector];
}
this.elements = elements;
};

All you really need to do is make sure your Constructor argument can distinguish between a string selector being passed in, and an object.
const Constructor = function(selector) {
if(typeof selector == "string"){
elements = document.querySelectorAll(selector);
this.elements = elements;
}
else{
this.elements = selector;
}
};
You can go further than this, but at a very minimum for the example given that works.
Live example below:
window.twentyFourJS = (function() {
let elements;
const Constructor = function(selector) {
if(typeof selector == "string"){
elements = document.querySelectorAll(selector);
this.elements = elements;
}
else{
this.elements = selector;
}
};
Constructor.prototype.addClass = function(className) {
elements.forEach( item => item.classList.add(className));
return this;
};
Constructor.prototype.on = function(event, callback, useCapture = false){
elements.forEach((element) => {
element.addEventListener(event, callback, useCapture);
});
return this;
}
const initFunction = function(selector){
return new Constructor(selector);
}
return initFunction;
})();
(function($){
$('.btn').on('click', function(event) {
console.log('I am clicked'); // This works
// I want to be able to do this
$(this).addClass('MyClass');
event.preventDefault();
});
})(twentyFourJS);
.MyClass{
background-color:red
}
<button class="btn">Click me</btn>

first You Need to Check for a string
case 1. $("div")
Then You need to Check for it's NodeType and for a window
case 1. var elm = document .getElementById("ID")
$(elm)
case 2. $(this) -- window
function $(selector){
var element;
if (typeof selector === 'string') {
element = document.querySelectorAll(selector)
}
if (element.nodeType || element=== window) element= [selector];
return element ;
}

Javascript: Chaining on elements like jQuery

I'm trying to replicate jQuery's element manipulation to a certain extent. Now what I have found to be very useful is the .first() selector. I would like to be able to chain functions like this;
getElement(selector).first().hasClass(className);
Now, there are 2 issues with how far I've gotten (Do note that my code example is minimised, so please, no comments about error-handling.)
var getElement = function(selector, parent) {
ret = document.querySelectorAll(selector);
this.element = ret;
this.hasClass = function(className) {
className.replace('.', '');
if(this.multiple())
{
console.log('Cannot use hasClass function on multiple elements');
return false;
}
};
this.first = function() {
this.element = this.element[0];
return this;
};
return this;
};
My current problem
If I call my function;
var $test = getElement('.something');
//result: nodelist with .something divs
If I call for the first element within the result;
$test.first();
//Result: First div, perfect!
However, now if I call $test again, it will replace the elements property with the result of first(), meaning I have "lost" my old values. I don't want to lose them, I only want the first() functions for that specific functionality. Then I want $test to return all elements again.
Also, recalling first() will now end up undefined, since there is only 1 element left within this as it has deleted the old elements from within the object.
Another attempt
Now, I've also tried to turn it around a bit by returning the first-child instead of the entire class object;
this.first = function() {
return this.element[0];
};
However, I will
$test.first().hasClass(className);
//Returns ERROR, method hasClass undefined
this is because .hasClass exists on the original this, which doesn't get returned anymore since I'm now returning the element.
I have tried to get something out of jQuery's library, though that just confused me more...
I have googled this subject, but with all the 'chaining methods' solutions I'm finding, all of them seem to be overwriting the original values of the object, which is not what I want to happen. One other solution actually required me to re-initiate the object over and over again, which did not seem very efficient to me... Any help is appreciated. I'm assuming I'm going about this completely the wrong way.
-- If you can help me, please do explain why your solution works. I really feel like if I understand this, my understanding of javascript can expand a lot further. I just need to get past this structural(?) issue.

A method like first() should not modify this, it should create a new object and return that. You only use return this; in methods that modify an element rather than returning information derived from the element.
this.first = function() {
return new getElement(this.element[0]);
};
And note that you have to use new getElement to create an object, not just getElement.
This also requires a change to the constructor, so it can accept either a selector string or an element:
var getElement = function(selector, parent) {
var ret = typeof selector == "string" ? document.querySelectorAll(selector) : [selector];
...
}
You should also consider doing this in proper OO fashion, by putting the methods in a prototype, rather than defining them in every object.
var getElement = function(selector, parent) {
var ret = typeof selector == "string" ? document.querySelectorAll(selector) : [selector];
this.element = ret;
};
getElement.prototype.hasClass = function(className) {
className.replace('.', '');
if (this.multiple()) {
console.log('Cannot use hasClass function on multiple elements');
return false;
}
};
getElement.prototype.first = function() {
return new getElement(this.element[0])
};

this in your outer function refers to the window / global object.
Instead, return the ret variable itself.
In the inner functions (which become the object's methods), this acts the way you expect it to.
Here's an alternative solution, which allows chaining, even after you've called the first method:
var getElement = function(selector, parent) {
var ret = typeof selector == 'string' ? document.querySelectorAll(selector)
: selector;
ret.hasClass = function(className) {
if(!this.classList) {
console.log('Cannot use hasClass function on multiple elements');
return false;
} else {
return this.classList.contains(className);
}
};
ret.first = function() {
return new getElement(this[0]);
};
return ret;
};
console.log(getElement('p').length); //2
console.log(getElement('p').first().innerHTML); //abc
console.log(getElement('p').first().hasClass('test')); //true
console.log(getElement('p').first().hasClass('nope')); //fase
console.log(getElement('p').hasClass('test')); //false (multiple elements)
<p class="test">
abc
</p>
<p>
def
</p>

Here is how I would approach this:
Create a constructor, say Search, tasked to find the elements based on the input. Using a constructor is proper OO Programming and you also have the advantage of defining methods once in the prototype and they can be accessed by all instances.
Ensure that the context (this) is an array-like object, with numeric properties and a length, so that you can easily iterate over every matched element in the traditional way (using for loops, [].forEach etc).
Create a function, say getElement, that will use the constructor and return the result without having to use the new keyword all the time. Since the function returns an instance of our constructor, you can chain the methods you want as you would normally do.
The method first uses the constructor to create a new instance instead of modifying the original, since its role is to return the first element, not delete everything but the first element.
Each time you come up with a new method you want your object to have, you can simply add it to the prototype of the constructor.
Snippet:
;(function () {
function Search (value) {
var elements = [];
/* Check whether the value is a string or an HTML element. */
if (typeof value == "string") {
/* Save the selector to the context and use it to get the elements. */
this.selector = value;
elements = document.querySelectorAll(value);
}
else if (value instanceof Element) elements.push(value);
/* Give a length to the context. */
this.length = elements.length;
/* Iterate over every element and inject it to the context. */
for (var i = 0, l = this.length; i < l; i++) this[i] = elements[i];
}
/* The method that returns the first element in a Search instance. */
Object.defineProperty(Search.prototype, "first", {
value: function () {
return new Search(this[0]);
}
});
/* The global function that uses the Search constructor to fetch the elements. */
window.getElement = (value) => new Search(value);
/* Create a reference to the prototype of the constructor for easy access. */
window.getElement.fn = Search.prototype;
})();
/* Get all elements matching the class, the first one, and the first's plain form. */
console.log(getElement(".cls1"));
console.log(getElement(".cls1").first());
console.log(getElement(".cls1").first()[0]);
/* ----- CSS ----- */
.as-console-wrapper {
max-height: 100%!important;
}
<!----- HTML ----->
<div id = "a1" class = "cls1"></div>
<div id = "a2" class = "cls1"></div>
<div id = "a3" class = "cls1"></div>
Example:
In this example, I'm adding a new method called hasClass to the prototype of the constructor.
/* The method that returns whether the first element has a given class. */
Object.defineProperty(getElement.fn, "hasClass", {
value: function (value) {
return this[0].classList.contains(value);
}
});
/* Check whether the first element has the 'cls2' class. */
console.log(getElement(".cls1").first().hasClass("cls2"));
<!----- HTML ----->
<script src="//pastebin.com/raw/e0TM5aYC"></script>
<div id = "a1" class = "cls1 cls2"></div>
<div id = "a2" class = "cls1"></div>
<div id = "a3" class = "cls1"></div>

I think the easiest would be to return a new class that contains the nodes you have selected. That would be the easiest solution, as you don't really want to mutate any of your previous selectors.
I made a small example, using some ES6 that makes a few things easier to work with, which also has a $ to initiate the selections being made.
You would notice that first of all, any selection that is made, is just calling the native document.querySelectorAll but returns a new Node class. Both first and last methods also return those elements.
Lastly, hasClass should work on all elements in the current nodes selections, so it will iterate the current node, and check all classes in there, this one returns a simple bool, so you cannot continue with the method chaining there.
Any method you wish to chain, should either:
return this object (the current node)
return an element of the this object as a new node so any further manipulations can be done there
const $ = (function(global) {
class Node extends Array {
constructor( ...nodes ) {
super();
nodes.forEach( (node, key) => {
this[key] = node;
});
this.length = nodes.length;
}
first() {
return new Node( this[0] );
}
last() {
return new Node( this[this.length-1] );
}
hasClass( ...classes ) {
const set = classes.reduce( (current, cls) => {
current[cls] = true;
return current;
}, {} );
for (let el of this) {
for (let cls of el.classList) {
if (set[cls]) {
return true;
}
}
}
return false;
}
}
global.$ = function( selector ) {
return new Node( ...document.querySelectorAll( selector ) );
};
return global.$;
}(window));
let selector = $('.foo');
let first = selector.first(); // expect 1
console.log(first[0].innerHTML);
let last = selector.last();
console.log(last[0].innerHTML); // expect 4
console.log( first.hasClass('foo') ); // expect true
console.log( first.hasClass('bar') ); // expect false
console.log( selector.hasClass('foo') ); // expect true
console.log( selector.hasClass('bar') ); // expect true
<div class="foo">1</div>
<div class="foo">2</div>
<div class="foo bar">3</div>
<div class="foo">4</div>

You can update getElement so it returns back again when you send it an element.
var getElement = function(selector, parent) {
var ret = null
if (typeof selector === "string") {
ret = document.querySelectorAll(selector);
} else {
ret = selector
}
this.element = ret;
this.hasClass = function(className) {
className.replace('.', '');
if (this.multiple()) {
console.log('Cannot use hasClass function on multiple elements');
return false;
}
};
this.first = function() {
this.element = getElement(this.element[0]);
return this;
};
return this;
};
var test = getElement(".foo");
console.log(test.first())
console.log(test.first().hasClass)
<div class="foo">1</div>
<div class="foo">2</div>
<div class="foo">3</div>
<div class="foo">4</div>

You can use .querySelectorAll(), spread element and Array.prototype.find(), which returns the first match within an array or undefined
const getElement = (selector = "", {prop = "", value = "", first = false} = {}) => {
const el = [...document.querySelectorAll(selector)];
if (first) return el.find(({[prop]:match}) => match && match === value)
else return el;
};
let first = getElement("span", {prop: "className", value: "abc", first: true});
console.log(first);
let last = getElement("span");
console.log(all);
<span class="abc">123</span>
<span class="abc">456</span>

How to replicate jQuery's $(this)?

I am creating a mini-library, sort of trying to reconstruct, at least partly, the way jQuery works for learning purposes and to understand better how object-oriented programming works.
I have recreated the jQuery methods click and addClass, but when I call them like:
$(".class1").click(function() {
$(".class1").addClass("class2"); // Works, but it adds class2 to all elements
this.addClass("class2"); // Doesn't work
});
I get an Uncaught Error saying this.addClass is not a function, which is normal, since I shouldn't be able to access another object's methods.
How is $(this) made in jQuery to mean the DOM element that triggered an event, so that in my case I can use it to add class2 only to the element clicked and not all elements that have the class class1?
P.S: I tried reading the jQuery file, but I feel like these waters are currently too deep for me.
Edit:
I always appreciate all the answers and the help I get on Stack Overflow, but telling me to use $(this) instead of this doesn't solve my issue, because $(this) doesn't exist in my code. I'm trying to learn how to create something like jQuery's $(this) & what's the logic behind it.
The click method is defined as follows:
$.prototype.click = function(callback) {
for (var i = 0; i < this.length; i++) {
this[i].onclick = function(event) {
callback.call(this, event);
}
}
};

With an extra 1.5 years of experience, this question becomes rather easy.
Alter $, so that, except string selectors, it can accept HTML elements.
Create a new instance of the object containing the HTML element given.
Call addClass with that as the context.
Code:
;(function() {
/* The object constructor. */
function ElementList(arg) {
/* Cache the context. */
var that = this;
/* Save the length of the object. */
this.length = 0;
/* Check whether the argument is a string. */
if (typeof arg == "string") {
/* Fetch the elements matching the selector and inject them in 'this'. */
[].forEach.call(document.querySelectorAll(arg), function(element, index) {
that[index] = element;
that.length++;
});
}
/* Check whether the argument is an HTML element and inject it into 'this'. */
else if (arg instanceof Element) {
this[0] = arg;
this.length = 1;
}
}
/* The 'click' method of the prototype. */
ElementList.prototype.click = function(callback) {
/* Iterate over every element and set the 'click' event. */
[].forEach.call(this, function(element) {
element.addEventListener("click", function(event) {
callback.call(this, event);
});
});
}
/* The 'addClass' method of the prototype. */
ElementList.prototype.addClass = function(className) {
/* Iterate over every element. */
[].forEach.call(this, function(element) {
/* Cache the classList of the element. */
var list = element.classList;
/* Add the specified className, if it doesn't already exist. */
if (!list.contains(className)) list.add(className);
});
}
/* The global callable. */
window.$ = function(arg) {
return new ElementList(arg);
}
})();
/* Example */
$("#b1").click(function() {
$(this).addClass("clicked");
console.log(this);
});
<button id="b1">Click</button>

You need to use call, apply, bind or some combination of those to set the callback's context to the DOM Node. Here is a contrived example of jquery's each method that sets the context of the callback using call:
var $ = {
each: function(selector, callback) {
var collection = Array.from(document.querySelectorAll(selector));
collection.forEach(function(element, index) {
// the magic...
callback.call(element, index, element);
});
}
}
$.each('.foo', function(idx, el) {
console.log(this.textContent);
});

this is the native JavaScript element and only exposes the native API. You need to pass it to the jQuery constructor in order to access jQuery's API
$(this).addClass("class2"); // This will work

One possible way (only selectors are accepted):
$ = function(selector) {
this.elements = '';//Select the element(s) based on your selector
this.addClass = function(klass) {
//apply your klass to you element(s)
return this;
};
this.click= function(handler) {
//Attach click event to your element(s)
return this;
};
return this;
};
Please keep in mind it's just an example.
Edit 1:
In your click method you are calling the handler in the wrong scope (the anonymous function scope). You need to use the outer scope:
$.prototype = {
click: function(callback) {
console.log(this.length);
var _self = this;
for (var i = 0; i < this.length; i++) {
this[i].onclick = function(event) {
//this here presents the anonymous function scope
//You need to call the handler in the outer scope
callback.call(_self, event);
//If you want to call the handler in the Element scope:
//callback.call(_self[i], event);
}
}
}
}
Note: In your example, this.addClass("class2"); doesn't work because jQuery calls the click handler in the Element scope not jQuery scope. Therefore, this presents the Element which dosen't have the addClass method;

Ok, I understand now your question. Let me try to help you again.
jQuery doesn't knows what DOM element do you use when you give it to selector. It doesn't parsing it or something else. Just save it to the internal property.
Very simplified code to understand:
$ = function(e) {
// finding object. For example "this" is object
if (typeof e !== 'object' || typeof e.className === 'undefined') {
if (typeof e == 'string') {
if (e[0] == '#') {
e = document.getElementById(e.substring(1));
} else if (e[0] == '.') {
e = document.getElementsByClassName(e.substring(1))[0];
} else {
// ... etc
}
}
// ... etc
}
var manager = {
elem: e,
addClass: function(newClass) {
manager.elem.className = manager.elem.className + ' ' + newClass;
return manager;
},
click: function(callback) {
// here is just simple way without queues
manager.elem.onclick = function(event) {
callback.call(manager, event);
}
}
}
return manager;
}

Creating an object like jQuery

For example, there is an object V which takes an element id, class or a tag name as a parameter and applies functions on it, like so.
var V = function(elem) {
// logic to getElementBy ID or class or tag name and return it
if(type === '#') {
// get by id
domElem = document.getElementById(elem.slice(1));
} else if(type === '.') {
// get by class
domElem = document.getElementsByClassName(elem.slice(1));
} else if(typeof type === 'string' && (type !== '#' || type !== '.')) {
// get by elem type
domElem = document.getElementsByTagName(elem);
}
return domElem;
}
So now when you get an element, like so: var myDiv = V('#someDivElement');
it will return you the div element. Now, I also run a method on the returned object. For example, I want to run a method asdf that simply appends a paragraph tag inside the div, like so:
V.prototype.asdf = function() {
this.appendChild('<p>I am an awesome child!</p>');
return this;
}
Ideally, it works when I do:
var myDiv = V('#someDivElement');
But the below line doesn't seem to execute.
myDiv.asdf();
What am I doing wrong here?

Your V('#someDivElement'); returns domElem, but asdf is defined on prototype of V.
What you might want is the following constructor function:
var V = function(elem) {
// logic to getElementBy ID or class or tag name and return it
if(type === '#') {
// get by id
this.domElem = document.getElementById(elem.slice(1));
} else if(type === '.') {
// get by class
this.domElem = document.getElementsByClassName(elem.slice(1));
} else if(typeof type === 'string' && (type !== '#' || type !== '.')) {
// get by elem type
this.domElem = document.getElementsByTagName(elem);
}
}
var myDiv = (new V('#someDivElement')).domElem;

you are defining V as a function that returns a DOM element, then trying to add a method onto V's prototype, then just calling it and getting a value.
But you can only use the prototype when you use V as a class - with the 'new' keyword. So try this:
var V = function(elem) {
this.elem = document.getElementsByTagName(elem);
... plus whatever else here ...
}
V.prototype.asdf = function() {
this.elem.innerHTML = "Hi Dave";
};
var myElem = new V('.someselectorOrElem');
myElem.asdf();
see how V is no longer used as a function but instead as a class constructor?
But.. it's not exactly the answer you're after, you want it to work just like jquery.
So taking the code above, you could, after that, also define a function called, say, $V, which constructs one and returns it, like this:
function $V(selectorOrElem) {
return new V(selectorOrElem);
}
and call it like this:
var myElem = $V(".someSelector");
then you have jquery-like behaviour.

What you are returning is simply a plain object from JS now go back and log the real jQuery, It's returning the object of the self that helps in chaining. so you need to wrap the object in your context. that's all.

Select parent object from a field in js

I am relatively new to OOP so I am not sure about the terminology.
I have created a DOM element as a field of an object (eg myObject.myElement) and I appended the element to the document. The object has a .mousemove() event attached (using jQuery). I want to be able to select the object (myObject) for whom the selected element (myElement) is a field so that I can access other fields of the object. There is more than one object and the event handler is the same for elements of different objects. Is it possible to select the parent object of the element? Do I need to give the element the same fields so that I can access the same data?
I want to be able to do something like this but maybe it is not that straightforward:
$('.bubble').on({mousemove: function () {
parentObject = this.parentObject();
alert(parentObject.otherDataField);
});
The element was created like this:
function bubbleObject(value)
{
this.value = value;
this.element = document.createElement('div');
$(this.element).appendTo('.bubbles');
}
myFirstBubble = new bubbleObject(10);
mySecondBubble = new bubbleObject(100);
and I need to be able to access the value field for the object (I am making it simpler as the code is pretty long and mostly irrelevant to my issue).
Do I need to do this:
function bubbleObject(value)
{
this.value = value;
this.element = document.createElement('div');
$(this.element).appendTo('.bubbles');
this.element.value = value; // add same value to element
}
or is there a better way?

A back reference to the parent could be better than copying values:
function bubbleObject(value)
{
this.value = value;
this.element = document.createElement('div');
$(this.element).appendTo('.bubbles');
this.element.parent = this;
}
However, using this way you have to use element.parent.value instead.

Another approach (as I mentioned before) is to scan all element-containing objects if they contain a specific element. If you don't have all these objects in an array you have to scan all window components (as I said, this is expensive):
function findElement(element) {
for (obj in window) {
if (typeof obj === 'object' && obj.myElement == element) {
return obj;
}
}
return null;
}
This is just an untested draft. And it would be so much better if you have a list of parent objects which you can use instead of window.
function findElement(element) {
for (int i = 0, l = objList.length; i < l; i++) {
if (typeof objList[i] === 'object' && objList[i].myElement == element) {
return objList[i];
}
}
return null;
}