I just want to share an experience with you all. So my problem was, that I came across the problem of binding javascript back-end objects to HTML front-end elements. Now, i have searched through google and read some stackoverflow articles about this problem, and many posts answer to this is to use jQuery.data(), however in my first attempts I did not succeed because there was something I did not know about jQuery's object creation method. My problem was that, I wanted to retrieve the stored data outside of the scope where i stored this, and jQuery always(i think) returns a new object reference when i write jQuery('selectorID'). So for example:
var ref1 = $('#myID');
var ref2 = $('#myID');
if(ref1 == ref2)
{
alert(true);
}
else
{
alert(false);
}
Will always alert false. However replacing the jQuery method with javascript's built-in getElementById() we will get the same reference! Hence the following code will always alert true!
var ref1 = document.getElementById("myID");
var ref2 = document.getElementById("myID");
if(ref1 == ref2)
{
alert(true);
}
else
{
alert(false);
}
The little morale of my story is that if you want to globally bind javascript objects to HTML elements and are thinking about using jQuery's data() method, store the data on the reference returned by javascript's built-in getElementById(). That way, whereever you retrieve the reference with getElementByID, you will always get the same reference and can get the data from it using jQuery's data() method.
My Questions:
Is my logic of thinking ok?
Is there a better way to globally bind javascript objects to HTML elements?
Whatever the reason behind the code you mention not working was, it was decidedly not the fact that jQuery gives you a new collection for every query. Given the HTML:
<div id="somediv"> foo bar </div>
the following Javascript works as expected:
var $ref1 = $('#somediv');
var $ref2 = $('#somediv');
console.log("$ref1:", $ref1);
console.log("$ref2:", $ref2);
// compare the collections / references
console.log("$ref1 == $ref2:", $ref1 == $ref2); // => false
console.log("$ref1 === $ref2", $ref1 === $ref2); // => false
// compare the referred DOM elements themselves
console.log("$ref1[0] == $ref2[0]:", $ref1[0] == $ref2[0]); // => true
console.log("$ref1[0] === $ref2[0]", $ref1[0] === $ref2[0]); // => true
$ref1.data('somedata', 'SOMEDATA');
console.log('$ref1->somedata:', $ref1.data('somedata')); // => SOMEDATA
console.log('$ref2->somedata:', $ref2.data('somedata')); // => SOMEDATA
The way I do it is something like this.
var ref1 = $('a');
var ref2 = $('div');
var equal = ref1.length === ref2.length;
if (equal) {
$.each(ref1, function(i) {
equal = equal && ref1[i] === ref2[i];
if (!equal) {
return false;
}
});
}
if (equal) {
alert(true);
} else {
alert(false);
}
ref1[0] === ref2[0] // Should return true
I think jQuery's instances are unique, so you can compare its matched items, which should be just one element when you reference an ID.
You could do something like this:
var ref1 = $('#myID')[0];
var ref2 = $('#myID')[0];
I dive into jQuery's source code, and find the constructor of jQuery. As follow:
// Define a local copy of jQuery
jQuery = function( selector, context ) {
// The jQuery object is actually just the init constructor 'enhanced'
return new jQuery.fn.init( selector, context, rootjQuery );
}
Whenever you use ref2 = $('#myID') to retrive a corresponding jQuery element, jQuery will create a new object to you. So the == will return false to you coz' the two element is completely different to js object engine.
Seems getElementById method is more fit your need. But I don't know how js engine perform its getElementById method.
Related
This is not for use in my project, Only for learning purposes.
In jQuery,
When we call $('h1'). it simply returns all the h1 elements from the document. Again when we make some action on an element like $('h1').hide(), it simply hides all the elements(cool ah?)
I want to learn this similar functionality, for example:
function app(elm){
const x = (typeof elm !== 'object') ? document.querySelectorAll(elm) : elm
return {
hide : function(){
x.forEach( target =>{
target.style.display = 'none';
});
}
}
}
This is a simple code here. So, If I call it like app('h1').hide(); it will hide all the h1 elements from the document. But if I call it like app('h1') it returns the object what I return that's normal.
In here I need all h1 elements from the document like jQuery. I mean It should work like this,
$('h1') === app('h1') //JQuery is equal to myCFunction (problem)
$('h1').hide === app('h1').hide() //jQuery is equal to myCFunction (solved)
[NOTE] Here is an article that is similar to my question but it's not my question answer.
Article Link
You can return x instead of a custom object, but before returning inject the hide function into x object's prototype like x.prototype.hide = function(){/*...*/}.
I think $("h1") does not return selected elements. It stores the selected elements. Instead we can have new function(getElement) to get select elements.Hope this code helps.
var App = function() {
var x ;
this.app = function (elem) {
x = document.querySelectorAll(elem);
return this;
}
this.hide = function(){
x.forEach(target => {
target.style.display = 'none';
});
return;
}
this.getElement = function(){
return x;
}
}
var $ = new App();
$.app("h1").hide();
console.log($.app("h1").getElement());
I've got a mostly working solution, but you still have to fix one small but annoying problem (see caveat 3). It's mostly done so I'll put it here anyway.
I think this is what you are looking for:
function app(selector) {
const retArr = document.querySelectorAll(selector); // The array to return
// Add proxies for all prototype methods of all elements
for (let e of retArr) {
let methods = getProtoMethods(e);
for (let mKey in methods) {
// Skip if the proxy method already exists in retArr
if (retArr[mKey] !== undefined) continue;
// Otherwise set proxy method
Object.defineProperty(retArr, mKey, {
value: function(...args) {
// Loop through all elements in selection
retArr.forEach(el => {
// Call method if it exists
if (el[mKey] !== undefined) el[mKey](...args);
});
}
});
}
}
return retArr;
// Gets all prototype methods for one object
function getProtoMethods(obj) {
let methods = {};
// Loop through all prototype properties of obj and add all functions
for (let pKey of Object.getOwnPropertyNames(Object.getPrototypeOf(obj))) {
// Skip properties that aren't functions and constructor
if (pKey !== "constructor" && typeof obj[pKey] === "function") {
methods[pKey] = obj[pKey];
}
}
return methods;
}
}
The idea is to put all the selected objects in an array, then define additional methods on the array. It should have all the method names of the selected objects, but those methods are actually proxies of those original methods. When one of these proxy methods is called, it calls the original method on all (see caveat 1) the selected objects in the array. But otherwise the returned object can just be used as a normal array (or more accurately, NodeList in this case).
However it's worth mentioning that there are several caveats with this particular implementation.
The list of proxy methods created is the union of the methods of all selected objects, not intersection. Suppose you selected two elements - A and B. A has method doA() and B has method doB(). Then the array returned by app() will have both doA() and doB() proxy methods. However when you call doA() for example, only A.doA() will be called because obviously B does not have a doA() method.
If the selected objects do not have the same definition for the same method name, the proxy method will use their individual definitions. This is usually desired behaviour in polymorphism but still it's something to bear in mind.
This implementation does not traverse the prototype chain, which is actually a major problem. It only looks at the prototypes of the selected elements, but not the prototypes of prototypes. Therefore this implementation does not work well with any inheritance. I did try to get this to work by making getProtoMethods() recursive, and it does work with normal JS objects, but doing that with DOM elements throws weird errors (TypeError: Illegal Invocation) (see here). If you can somehow fix this problem then this would be a fully working solution.
This is the problematic recursive code:
// Recursively gets all nested prototype methods for one object
function getProtoMethods(obj) {
let methods = {};
// Loop through all prototype properties of obj and add all functions
for (let pKey of Object.getOwnPropertyNames(Object.getPrototypeOf(obj))) {
// Skip properties that aren't functions and constructor
// obj[pKey] throws error when obj is already a prototype object
if (pKey !== "constructor" && typeof obj[pKey] === "function") {
methods[pKey] = obj[pKey];
}
}
// If obj's prototype has its own prototype then recurse.
if (Object.getPrototypeOf(Object.getPrototypeOf(obj)) == null) {
return methods;
} else {
return {...methods, ...getProtoMethods(Object.getPrototypeOf(obj))};
}
}
Sorry I cannot solve your problem 100%, but hopefully this at least somewhat helpful.
Is it possible to store the reference to an element in an array or object without having a unique ID on the element?
I am having trouble with storing a subtable in another table so I can reference it later. I get the table by class with this code:
$(this).parent('tr').parent().find('.tableSomeTable');
Is the only solution to have unique id's on each element and use the .selector method?
More of my code. Abit simplified.
var rows = [];
var historyLoad;
$(document).on("click", '.details-control', function (e) {
var t = $(this);
var tr = t.closest('tr');
var row = t.parent().parent().parent().DataTable().row(tr);
var id = t.closest('tr').attr('id');
var object = {
id: id,
btnHistory: t.parent('tr').next().find('#btnHistory'),
tblHistory: t.parent('tr').parent().find('.tableHistory'),
historyLoad: historyLoad
};
if ($.inArray(id, rows) > -1) {
loadData = false;
}
else {
loadData = true;
loadHistory(object);
rows.push(object);
}
};
Here is where I am having trouble retrieving the correct elements. And I also want to save the ajaxHistory element to my object (which is working fine).
This code is not working, but if I change it to $(result.btnHistory.btnHistory.selector) I get the object. But this doesn't seem to work very good with multiple rows.
function loadHistory(result) {
result.ajaxHistory = $.ajax({
...
beforeSend: function () {
$(result.btnHistory).html(<loading txt>);
$(result.tblHistory).find('tbody').html(<loading txt>);
},
....
success: function (data) {
if (data.TotalRecordCount > 0) {
$(result.tblHistory).find('tbody').html('');
$.each(data.Records, function (e, o) {
$(result.tblHistory).find('tbody').append(<data>)
});
}
else {
$(result.tblHistory).find('tbody').html(<txt no records>);
}
$(result.btnHistory).html(<txt loading done>));
},
First off, if you are trying to find the parent table, try
var $myObj = $(this).closest('table.tableSomeTable');
instead of navigating parents.
As far as storing the jQuery reference, define a variable and then store it. The above will store the object in $myObj but that is locally scoped. If you need a global variable then define it globally and just assign it here. If you want to define it as a property within an object then define it that way. It really comes down to a scope question at this point.
EDIT: Just saw your added content.
First off, don't name it 'object'. This may run into key word issues. Use var myObj or similar instead. Next, object.btnHistory is a reference to a jQuery object. So, when you pass it to loadHistory, you do not need to apply the $(...) again. Just use the reference directly: result.btnHistory.html(...). A good habit to get into is prepending you jQuery variables with $ so you remember it is already a jQuery variable.
The .find() method returns a jQuery object. So the answer is, yes, you can store this return object in a variable:
var $yourObject = $(this).parent('tr').parent().find('.tableSomeTable');
I'd like to 'proxy' (not sure if that's the term at all) a function inside a function object for easy calling.
Given the following code
function Soldier() {
this.el = $("<div></div>").addClass('soldier');
this.pos = this.el.position; // $(".soldier").position(), or so I thought
}
In the console:
s = new Soldier();
$("#gamemap").append(s.el); // Add the soldier to the game field
s.pos === s.el.position // this returns true
s.el.position() // Returns Object {top: 0, left: 0}
s.pos() // Returns 'undefined'
What am I doing wrong in this scenario and is there an easy way to achieve my goal (s.pos() to return the result of s.el.position()) ?
I thought about s.pos = function() { return s.el.position(); } but looks a bit ugly and not apropriate. Also I'd like to add more similar functions and the library will become quite big to even load.
When you're calling s.pos(), its this context is lost.
You can simulate this behavior using call():
s.pos.call(s); // same as s.pos()
s.pos.call(s.el); // same as s.el.position()
This code is actually ok:
s.pos = function() { return s.el.position(); }
An alternative is using bind():
s.pos = s.el.position.bind(el);
You can use the prototype, that way the functions will not be created separately for every object:
Soldier.prototype.pos = function(){ return this.el.position(); }
I'd recommend to use the prototype:
Soldier.prototype.pos = function() { return this.el.position(); };
Not ugly at all, and quite performant actually.
If you want to directly assign it in the constructor, you'll need to notice that the this context of a s.pos() invocation would be wrong. You therefore would need to bind it:
…
this.pos = this.el.position.bind(this.el);
It's because the context of execution for position method has changed. If you bind the method to work inside the element context it will work.
JS Fiddle
function Soldier() {
this.el = $("<div></div>").addClass('soldier');
this.pos = this.el.position.bind(this.el);
}
var s = new Soldier();
$("#gamemap").append(s.el);
console.log(s.pos());
I ran yesterday in a problem with a jquery-selector I assigned to a variable and it's driving me mad.
Here is a jsfiddle with testcase:
assign the .elem to my obj var
log both lengths to the console. Result => 4
Remove #3 from the DOM
log obj to the console => the removed #3 is still there and the length is still 4.
I figured out that jquery query is snapshotted? to the variable and can't?won't? be updated
log .elem to the console.. yep Result => 3 and the #3 is gone
Now I update .elem with a new width of 300
logging obj & obj.width gives me 300.. So the snapshot has been updated ? What's interesting is that 3 of the 4 divs have the new width, but the removed #3 doesn't...
Another test: Adding a li element to the domtree and logging obj and .elem.
.elem does have the new li and obj doesn't, because it's still the old snapshot
http://jsfiddle.net/CBDUK/1/
Is there no way to update this obj with the new content?
I don't want to make a new obj, because in my application there is a lot information saved in that object, I don't want to destroy...
Yeah, it's a snapshot. Furthermore, removing an element from the page DOM tree isn't magically going to vanish all references to the element.
You can refresh it like so:
var a = $(".elem");
a = $(a.selector);
Mini-plugin:
$.fn.refresh = function() {
return $(this.selector);
};
var a = $(".elem");
a = a.refresh();
This simple solution doesn't work with complex traversals though. You are going to have to make a parser for the .selector property to refresh the snapshot for those.
The format is like:
$("body").find("div").next(".sibling").prevAll().siblings().selector
//"body div.next(.sibling).prevAll().siblings()"
In-place mini-plugin:
$.fn.refresh = function() {
var elems = $(this.selector);
this.splice(0, this.length);
this.push.apply( this, elems );
return this;
};
var a = $(".elem");
a.refresh() //No assignment necessary
I also liked #Esailija solution, but seems that this.selector has some bugs with filter.
So I modified to my needs, maybe it will be useful to someone
This was for jQuery 1.7.2 didn`t test refresh on filtered snapshots on higher versions
$.fn.refresh = function() { // refresh seletor
var m = this.selector.match(/\.filter\([.\S+\d?(\,\s2)]*\)/); // catch filter string
var elems = null;
if (m != null) { // if no filter, then do the evarage workflow
var filter = m[0].match(/\([.\S+\d?(\,\s2)]*\)/)[0].replace(/[\(\)']+/g,'');
this.selector = this.selector.replace(m[0],''); // remove filter from selector
elems = $(this.selector).filter(filter); // enable filter for it
} else {
elems = $(this.selector);
}
this.splice(0, this.length);
this.push.apply( this, elems );
return this;
};
Code is not so beautiful, but it worked for my filtered selectors.
Clean and generic solution worked properly with jQuery 3.4.1:
My solution is to do the following:
Intercept the selector at the time of jQuery object initialization and in the same time maintain all other jQuery functionalities transparently all this using inheritance
Build refresh plugin that make use of the new "selector" property we added during initialization
Definition:
$ = (function (originalJQuery)
{
return (function ()
{
var newJQuery = originalJQuery.apply(this, arguments);
newJQuery.selector = arguments.length > 0 ? arguments[0] : null;
return newJQuery;
});
})($);
$.fn = $.prototype = jQuery.fn;
$.fn.refresh = function ()
{
if (this.selector != null && (typeof this.selector === 'string' || this.selector instanceof String))
{
var elems = $(this.selector);
this.splice(0, this.length);
this.push.apply(this, elems);
}
return this;
};
Usage:
var myAnchors = $('p > a');
//Manipulate your DOM and make changes to be captured by the refresh plugin....
myAnchors.refresh();
//Now, myAnchors variable will hold a fresh snapshot
Note:
As optimization, object selectors don't need refresh as they are pass by reference by nature so, in refresh plugin, we only refresh if the selector is a string selector not object selector for clarification, consider the following code:
// Define a plain object
var foo = { foo: "bar", hello: "world" };
// Pass it to the jQuery function
var $foo = $( foo );
// Test accessing property values
var test1 = $foo.prop( "foo" ); // bar
// Change the original object
foo.foo = "koko";
// Test updated property value
var test2 = $foo.prop( "foo" ); // koko
Jquery .selector is deprecated, it's better to remeber string with selector value to some variable at the moment when you assign
function someModule($selector, selectorText) {
var $moduleSelector = $selector;
var moduleSelectorText = selectorText;
var onSelectorRefresh = function() {
$moduleSelector = $(moduleSelectorText);
}
}
https://api.jquery.com/selector/
You can also return the JQuery selector in a function, and save this function into the variable. Your code will look a bit different but it works. Every time when you execute the function, your jquery selector will search the DOM again.
In this example I used an arrow function without brackets which will return whatever is next to arrow. In this case it will return the JQuery collection.
const $mySelector = () => $('.selector');
console.log($mySelector().last().text());
$('.parent').append('<li class="selector">4</li>')
console.log($mySelector().last().text()); //RETURNS 4 not 3
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<ul class="parent">
<li class="selector">1</li>
<li class="selector">2</li>
<li class="selector">3</li>
</ul>
If you use remove() it will remove only a part of the DOM but not all the children or related, instead if you use empty() on the element the problem is gone.
E.G.:
$('#parent .child).find('#foo').empty();
Maybe it can be useful to someone!
I want to change the method DomElement.appendChild() to work differently when applied on an Object that I have created:
// using MooTools;
var domElement = new Class({...});
var MyObject = new domElement(...);
$(document).appendChild(MyObject); // Error
// I want to add to (extend) appendChild, to do something specific, when:
alert(MyObject instanceof domElement); // true
I could do this by modifying the mootools.js, but I want to avoid this at all costs, because I am certain one day, some other developer will overwrite the js file with an updated version, and I will be imprisoned for murder.
Please, keep me out of jail!
I dont know about MooTools, but there is a simple way in native JS to do this..
var orgAppendChild = document.appendChild;
document.appendChild = localAppendHandler;
var domElement = new Class({...});
var MyObject = new domElement(...);
// document.appendChild(MyObject);
var ss = document.createElement('tr');
document.appendChild (ss);
function localAppendHandler(MyObject)
{
if (MyObject instanceof domElement)
UrCustomRoutine(MyObject )
else
orgAppendChild(MyObject);
}
function UrCustomRoutine(MyObject ){
//your custom routine
}
Hope this helps
Update:
From your further explanation (handling appendChild of any DOM element), i understand that there is no generic way of defining local hanlders to trap the event.
But there is a workaround (this is very ugly i know). Means you have to define a LocalHandler for the DOM element before you are goin to use the appendChild .
Before doing this
document.getElementByID('divTarget').appendChild()
you have to reassign the localhandler to the element you need to access
orgAppendChild = document.getElementById('divTarget').appendChild;
document.getElementById('divTarget').appendChild = localAppendHandler;
var sss = document.createElement('table');
document.getElementById('divTarget').appendChild(sss);
Another Alternative:
If you wanted to keep it simple, i suggest this alternate way. Create AppendChild local method which accepts object and the node name as param.
function AppendChild(MyObject ,Node)
{
if (MyObject instanceof domElement)
//your custom routine
else if (Node=="" && (MyObject instanceof domElement==false))
document.appendChild(MyObject);
else if (Node!="" && (MyObject instanceof domElement==false))
eval( "document.getElementById('" + Node + "').appendChild(MyObject);");
}
And
If you wanted to append DOM element to document
AppendChild(DOMelement,"")
If you wanted to append DOM element inside other
container
AppendChild(DOMelement,"divTarget")
If you wanted to process your custom object
AppendChild(customObject,"")
this is the best way to do this.
you ought to look at using object.toElement() in your class
http://blog.kassens.net/toelement-method
then just use document.body.inject(instanceObject);
var originAppend = Element.prototype.appendChild;
Element.prototype.appendChild = function(el){
// do something to el
originAppend.call(this, el);
}