I need function to click on a range of check boxes. I do however not always know what i is. I tried a write a forEach loop, but it does not work:
This for loop works:
function check Boxes() {
for (let i = 0; i < 249; i++) {
document.getElementsByClassName("inventoryCbox")[i].click();
}
}
and this is the non-working for loop. I think that maybe my syntax is wrong.
checkBoxes();
var boxes = document.getElementsByClassName("inventoryCbox");
function checkBoxes(node) {
node.forEach(function(boxes) {
boxes.click()
});
}
This will check all the checkboxes with the class 'inventoryCbox':
document.querySelectorAll(".inventoryCbox").forEach(node => node.click())
node in your checkBoxes function is undefined, because you're not passing anything into the function. Also, your code has you calling checkBoxes before you assign anything to boxes. You probably meant to use boxes directly:
// This *before* `checkboxes`
var boxes = document.getElementsByClassName("inventoryCbox");
checkBoxes();
function checkBoxes() { // <== No parameter
boxes.forEach(function(box) {
//^^^^^ ^^^
box.click()
// ^^^
});
}
But that still has a problem: The HTMLCollection returned by getElementsByClassName doesn't have forEach reliably cross-browser. (The NodeList returned by querySelectorAll has it on modern browsers, but not HTMLCollection.)
You can add it if you like:
if (typeof HTMLCollection !== "undefined" &&
HTMLCollection.prototype &&
!HTMLCollection.prototype.forEach) {
// Yes, direct assignment is fine here, no need for `Object.defineProperty`
HTMLCollection.prototype.forEach = Array.prototype.forEach;
}
Then the updated code above would work.
Or stick with your existing loop, or use Array.prototype.forEach directly:
function checkBoxes() { // <== No parameter
Array.prototype.forEach.call(boxes, function(box) {
box.click()
});
}
My answer here goes into details for adding not just forEach but iterability to HTMLCollection (and NodeList in environments that haven't implemented iterability for NodeList yet).
If you want to click on all elements selected by some class, you can use this example
var els = document.querySelectorAll('.inventoryCbox');
for (i = 0; i < els.length; ++i) {
els[i].click();
};
Related
I'm new to JavaScript/HTML/CSS and I can't spot the mistake I'm doing in this JavaScript function. Our teacher told us to use the addEventListener method cause it has some notable advantages.
This is my entire script with the problematic function
var espandi = function (e) {
var toHide = document.getElementsByClassName("optional");
for (var index = 0; index < toHide.length; index++)
toHide[index].style.display = "none";
var toShow = e.target.getElementsByClassName("optional");
for (index = 0; index < toShow.length; index++)
toShow[index].style.display = "block";
}
var expansibleObjects = document.getElementsByClassName("singleresult");
for (var index = 0; index < expansibleObjects.length; index++)
expansibleObjects[index].AddEventListener("click",espandi);
The fact is the line e.target.getElementsByClassName gets me an error of this type
Uncaught TypeError: Cannot read properties of undefined (reading 'getElementsByClassName').
On the contrary, if I set the function with the property "onclick" directly on the element the function works perfectly. So I think the problem it's about referring to the calling object using e.target
Update 1
First of all, I want to say that this is a project for university and I cannot publish the whole code, it would be risky for my exam.
Then there are more issues apparently. First of all with the method getElementsByClassName() applied on document it seems that he can get the Collection of Elements but then if I try to print the single Element it gives me undefined on the log. Here's the code:
var list = document.getElementsByClassName("prova");
if (list[0]) {
console.log("Assigning using \"list[0]\" as check");
list[0].onclick = espandi();
list[0].addEventListener("click",espandi);
console.log("finished adding listeners");
}
else if(list.item(0)){
console.log("Assigning using \"list.item(0)\" as check");
list.item(0).onclick = espandi();
list.item(0).addEventListener("click",espandi);
console.log("finished adding listeners");
}
else console.log("failed assignment");
console.log("printing list");
console.log(list);
console.log("printing list[0]");
console.log(list[0]);
console.log("printing list.item(0)");
console.log(list.item(0));
and here's the log output:
log output
Apparently the only way I succesfully make my script work is editing the function this way:
function espandi (caller) {
var toHide = document.getElementsByClassName("optional");
for (var index = 0; index < toHide.length; index++)
toHide[index].style.display = "none";
var toShow = caller.getElementsByClassName("optional");
for (index = 0; index < toShow.length; index++)
toShow[index].style.display = "block";
}
and then assigning it to elements directly using the "onclick" HTML attribute, like this:
<table class="prova" onclick="espandi(this)">
so that the parameter "caller" refers to the element who actually triggered the function espandi. The problem is I really want to know 2 things:
how to refer to the caller using an EventHandler function (in the case of method .addEventListener()) and a normal function (in the case of the attribute .onclick of the desired element) in JS.
how to manage the method getElementByClassName() and the collection returned by itself.
In the end, just to sum up, now I have problems with assigning the event listeners and also with referring to the caller without using a parameter like this in the HTML code I showed you.
You are calling espandi instead of assign it to onclick handler.
So you need to remove the () and do expansibleObjects[index].onclick = espandi;
Anyway in your question I don't see any e.target.addEventListener() so when you say The fact is the line e.target.addEventListener() gets me an error I don't understand what you mean, maybe you have to add more code.
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.
I am attempting to bind a dblclick event to divs in a nodeList which I am iterating through.
Here is the code:
var elems = document.getElementsByClassName("click");
currentLocation = elems[0].id;
for (var i=0; i<elems.length; i++){
$(elems[i]).dblclick(function() {
if((elems[i].id) != currentLocation){
badAnswer = true;
alert(badAnswer);
}
});
}
currentLocation is a global variable set to the first element id of the node list. badAnswer is also a global boolean set to false. If a element is double clicked that matches an element other than the currentLocation global, badAnswer is set to true.
Currently I receive a undefined error, which I tried to remedy by creating a local variable inside of the event handler. This didn't seem to work either and badAnswer is always true on double click as the elementID is always equal to the ID value of the last element.
Is there a better way to do this?
Yes, there is a much better way:
var currentLocation = $(".click")[0].id;
$(".click").on("dblclick", function() {
if (this.id != currentLocation) {
badAnswer = true;
}
});
$('.click').dblClick(function() {
if(this.id != currentLocation) {
...
}
});
You're already using jQuery so you might as well use the selectors...much easier!
I've been trying to understand why whenever value of the array I click, it always add the class "foo".
Example: I clicked on London (cities[1], right?) and it added the class foo.
var cities = [
document.getElementById('Paris'),
document.getElementById('London'),
document.getElementById('Berlin')
];
for (var i = 0; i < cities.length; i++) {
cities[i].onclick = test;
function test(){
if(cities[i] === cities[0]) {
el.classList.add("foo");
}
}
}
EDIT: my original answer was incorrect, this updated one is right. addEventListener returns nothing. Instead, you should use some kind of wrapper to add and remove your listeners, again so that you don't waste resources on listeners that you aren't using:
function on (element, eventName, callback) {
element.addEventListener(eventName, callback);
return function unregister () {
element.removeEventListener(callback);
}
}
function test (event) {
if (event.currentTarget===cities[0]) {
event.target.classList.add('foo');
}
}
var listenerRemovers = cities.map(function (city) {
return on(city, 'click', test);
});
Now you can remove any of these listeners by calling the corresponding function in your listenerRemovers array:
listenerRemovers.forEach(function (unRegisterFunc) { unRegisterFunc(); });
ORIGINAL WRONG ANSWER:
For what it's worth, you're probably better off using .map in a case like this, since best practice is to keep a reference to the event listeners so you can cancel them if needed.
function test (event) {
if (event.currentTarget===cities[0]) {
event.target.classList.add('foo');
}
}
var listenerHandlers = cities.map(function (city) {
return city.addEventListener('click', test);
});
This is happening because you are setting the event functions inside a loop. Each function is using the same value of i.
Try to use this instead of trying to cities[i] inside the function.
function test(){
if(this === cities[0]) {
el.classList.add("foo");
}
}
The easiest approach to achieve this functionality is to use jQuery, here is the idea:
In html tags, give those cities a common class, e.g. class="city"
$('.city').click(function(){$('.city').addClass('foo')});
jQuery saves you more time and coding efforts.
The problem is you are trying to assign a function to a DOM attribute. You are not registering a listener but modifying the DOM. If you wish to do it this way, you must assign the onclick as cities[i].onclick = 'test()'
Also, you should move the function test outside of the for loop to look like the following. The problem is the function test is being declared many times, each with a different 'i' value.
for (var i = 0; i < cities.length; i++) {
cities[i].onclick = 'test(this)';
}
function test(el){
if(cities[i] === cities[0]) {
el.classList.add("foo");
}
}
Here is my code:
var b = $(slipStream.conf.mainVis).find('p#prev');
b.click(function() {
slipStream.slideLeft();
return false;
});
b = $(slipStream.conf.mainVis).find('p#next');
b.click(function() {
slipStream.slideRight();
return false;
});
b = $(slipStream.conf.controls).find('li img');
console.log(b);
for (var l in b) {
l.click(function() {
var visIndex = l.index();
console.log(visIndex);
});
};
The first two bindings go through, no problem. But I can't loop through a collection and bind something to each member? (the console is telling me that "l.click is not a function.") Is this a limitation of jQuery or is my code off? This seems like it would be the way to do it, though...
When you enumerate over a jQuery object, the values being enumerated are actual DOM nodes and not jQuery wrappers. Therefore, they don't have a click method but you can wrap them again to get all the usual functionality.
Of course this is not necessary because you can simply attach a wrapper directly from your initial jQuery instance:
$(slipStream.conf.controls).find('li img').click(function() {
var visIndex = $(this).index();
console.log(visIndex);
});
This is the classic "loop variables don't work properly in callbacks" bug.
Your variable l no longer has the originally supplied value by the time the callback is invoked - it has whatever final value was assigned in the last pass through the loop.
[FWIW, l isn't actually a jQuery object, so you have to wrap it - $(l) to use it with jQuery]
The usual fix to the loop bug is to create an additional closure that returns a function bound to the current value:
for (var l in b) { // NB: don't use `for ... in ...` on array-like objects!
var make_cb = function(n) {
return function() {
var visIndex = $(n).index();
console.log(visIndex);
}
}
$(l).click(make_cb(l));
};
Fortunately, you don't need a loop at all - you can have jQuery automatically add the callback to every element by itself:
b = $(slipStream.conf.controls).find('li img');
b.click(function() {
var visIndex = $(this).index();
console.log(visIndex);
});
Could it be that the problem is the forloop. .click is part of the jQuery, so you must be sure that it's called on element that is wrapper with jQuery.
$.each(b, function (index, element) {
$(element).click(function() {
});
};
With each() you can iterate through a set of jQuery objects:
$(slipStream.conf.controls).find('li img').each(function(){
$(this).click(function() {
var visIndex = $(this).index();
console.log(visIndex);
});
});
$(this) will match the currently indexed object from the collection.