Javascript one function how I see another function variable? - javascript

The following is javascript code, the purpose is simulating jquery nextAll() function. Now the problem is that when I use function as argument, but it cannot see aLists variable in _nextAll() function.
function _nextAll(func) {
var aLists = document.getElementsByTagName("*");
var i = 0;
var temp = [];
while (i < aLists.length) {
if (func) { //if aLists[i].id = "one" replace func, this work
var j = i;
while (j < aLists.length) {
temp.push(aLists[j + 1]);
j++;
}
}
i++;
}
return temp;
}
var temp = _nextAll(function(){
if (aLists[i].id = "one"){ //aLists[i] cannot be seen in anonymous function
return true;
}
});
for (i = 0; i < temp.length; i++) {
temp[i].style.color = "orange";
}

You should pass the selector to _nextAll, have the function select the first element (or every element) matching the selector, then iterate over each element that comes after it:
function _nextAll(sel) {
let el = document.querySelector(sel);
const elements = [];
while (el = el.nextElementSibling) {
elements.push(el);
}
return elements;
}
for (const el of _nextAll('#one')) {
el.style.color = "orange";
}
<div>a</div>
<div>b</div>
<div id="one">c</div>
<div>d</div>
<div>e</div>

you have options to make the two functions see the same variable
1- you can define the variables outside the two functions and you can access the same from the two function
2-pass all the variable you want to share to the function parameters

Related

JavaScript remove an IIFE event listener

I'm trying to remove click events from a list of id's after adding them with an IIFE like this
function setupPlayer(player){
var squareState = {};
for (i = 0; i < allSquares.length; i++) {
if(allSquares[i].innerHTML === "") {
// set up a click event for each square
document.getElementById(allSquares[i].getAttribute('id')).addEventListener('click', (clickSquare)(i));
}
}
}
The clickSquare function returns
function clickSquare(i){
var num = i;
return function() {
document.getElementById(allSquares[num].getAttribute('id')).innerHTML=player;
}
}
Then I try to remove them with
function removeClickEvents(){
for (let i = 0; i < allSquares.length; i++) {
document.getElementById(allSquares[i].getAttribute('id')).removeEventListener('click', clickSquare);
}
}
I've tried naming the returned anonymous function and using removeEventListener on that to no avail.
To remove event listener from a DOM element you need to pass the same function you used while adding event listener, as the parameter.
In javascript when you create an object it creates a new instance of that object class, so it won't be equal to another object even if it is created with same parameters
Example:
{} != {} // returns true
[] != [] // returns true
Same goes with function, whenever you write function (){} it creates a new instance of Function class.
Example:
function a() {
return function b() {}
}
a() != a() // returns true
Solution:
So for you to be able to remove the event listeners, you will have to store the functions you have passed to addEventListener
var listeners = [];
function setupPlayer(player) {
var squareState = {};
for (i = 0; i < allSquares.length; i++) {
if(allSquares[i].innerHTML === "") {
listeners[i] = clickSquare(i);
document.getElementById(allSquares[i].getAttribute('id')).addEventListener('click', listeners[i]);
}
}
}
function clickSquare(i) {
var num = i;
return function() {
document.getElementById(allSquares[num].getAttribute('id')).innerHTML=player;
}
}
function removeClickEvents() {
for (let i = 0; i < allSquares.length; i++) {
if(listeners[i]) {
document.getElementById(allSquares[i].getAttribute('id')).removeEventListener('click', listeners[i]);
}
}
}
From your code where you are using
document.getElementById(allSquares[i].getAttribute('id'))
I am assuming that allSquares[i] is a DOM element already, your code can be more simplified
var listeners = [];
function setupPlayer(player) {
var squareState = {};
for (i = 0; i < allSquares.length; i++) {
if(allSquares[i].innerHTML === "") {
listeners[i] = clickSquare(i);
allSquares[i].addEventListener('click', listeners[i]);
}
}
}
function clickSquare(i) {
var num = i;
return function() {
allSquares[num].innerHTML=player;
}
}
function removeClickEvents() {
for (let i = 0; i < allSquares.length; i++) {
if(listeners[i]) {
allSquares[i].removeEventListener('click', listeners[i]);
}
}
}
The function is being called immediately at (clickSquare)(i). At code at Question allSquares appears to be the element itself, clickSquare function can be referenced directly and event.target can be used within event handler to reference the current element in allSquares collection
let player = 123;
setInterval(() => player = Math.random(), 1000);
onload = () => {
let allSquares = document.querySelectorAll("div[id|=square]");
let button = document.querySelector("button");
button.onclick = removeClickEvents;
function setupPlayer(player) {
var squareState = {};
for (let i = 0; i < allSquares.length; i++) {
if (allSquares[i].innerHTML === "click") {
// set up a click event for each square
allSquares[i].addEventListener('click', clickSquare);
}
}
}
function clickSquare(event) {
console.log(event.target);
event.target.innerHTML = player;
}
function removeClickEvents() {
for (let i = 0; i < allSquares.length; i++) {
allSquares[i].removeEventListener('click', clickSquare);
}
}
setupPlayer(player);
}
<div id="square-0">click</div>
<div id="square-1">click</div>
<div id="square-2">click</div>
<button>remove events</button>

Value being undefined? [duplicate]

I'm appending onclick events to elements that I'm creating dynamically. I'm using the code below, this is the important part only.
Test.prototype.Show= function (contents) {
for (i = 0; i <= contents.length - 1; i++) {
var menulink = document.createElement('a');
menulink.href = "javascript:;";
menulink.onclick = function () { return that.ClickContent.apply(that, [contents[i]]); };
}
}
First it says that it's undefined. Then I changed and added:
var content = content[i];
menulink.onclick = function () { return that.ClickContent.apply(that, [content]); };
What is happening now is that it always append the last element to all onclick events( aka elements). What I'm doing wrong here?
It's a classical problem. When the callback is called, the loop is finished so the value of i is content.length.
Use this for example :
Test.prototype.Show= function (contents) {
for (var i = 0; i < contents.length; i++) { // no need to have <= and -1
(function(i){ // creates a new variable i
var menulink = document.createElement('a');
menulink.href = "javascript:;";
menulink.onclick = function () { return that.ClickContent.apply(that, [contents[i]]); };
})(i);
}
}
This immediately called function creates a scope for a new variable i, whose value is thus protected.
Better still, separate the code making the handler into a function, both for clarity and to avoid creating and throwing away builder functions unnecessarily:
Test.prototype.Show = function (contents) {
for (var i = 0; i <= contents.length - 1; i++) {
var menulink = document.createElement('a');
menulink.href = "javascript:;";
menulink.onclick = makeHandler(i);
}
function makeHandler(index) {
return function () {
return that.ClickContent.apply(that, [contents[index]]);
};
}
};
A way to avoid this problem altogether, if you don't need compatibility with IE8, is to introduce a scope with forEach, instead of using a for loop:
Test.prototype.Show = function (contents) {
contents.forEach(function(content) {
var menulink = document.createElement('a');
menulink.href = "javascript:;";
menulink.onclick = function() {
return that.ClickContent.call(that, content);
};
});
}

javascript could not achieve the return

I had made this function, and this is new yet, and I don't really know how to handle this roughly.
var $;
(function() {
$ = function(e) {
return new query(e);
};
var query = function(e) {
var e = document.querySelectorAll(e), i;
for (i = 0; i < e.length; i++) {
this[i] = e[i];
}
this.length = e.length;
return this;
};
$.fn.prototype = {
hide: function() {
var i;
for (i = 0; i < this.length; i++) {
this[i].style.display = 'block';
}
return this;
},
hasClass: function (klass) {
var e = this, i;
var t = [];
for (i = 0; i < e.length; i++) {
var k = e[i].className;
var array = k.split(' ');
// If the element has the class, add it for return
if (array.indexOf(klass) > -1) {
t.push(e[i]);
}
}
// Return the list of matched elements
return t;
}
}
} ());
window.onload = function() {
$(".element").hasClass("someClass").hide();
}
So yeah, that's the code above. I think I have matched the class, but what the problem is, It's not returning the elements. I'm new to prototyping so please don't be harsh. I really need to fix this one. Please don't tell me to go and have jquery. I don't want to use that massive library just because I want some css selectors.
this inside the function isn't the current element.
hasClass: function (klass) {
var e = this, i;
var t = [];
for (i = 0; i < e.length; i++) {
var k = e[i].className;
var array = k.split(' ');
// If the element has the class, add it for return
if (array.indexOf(klass) > -1) {
t.push(e[i]);
}
}
// Return the list of matched elements
return t;
}
and that is why your script do not return the element.
ALSO:
You tried to use jQuery's method to add your own functions in library, but actually this will not work, as you're writing pure js, not jquery, and you need to do many thing to make it work like jQuery.
$.fn.prototype = {
hide: function() {
var i;
for (i = 0; i < this.length; i++) {
this[i].style.display = 'block';
}
return this;
},
hasClass: function (klass) {
var e = this, i;
var t = [];
for (i = 0; i < e.length; i++) {
var k = e[i].className;
var array = k.split(' ');
// If the element has the class, add it for return
if (array.indexOf(klass) > -1) {
t.push(e[i]);
}
}
// Return the list of matched elements
return t;
}
}
}
The problem here is this line: $.fn.prototype = {};. There is no $.fn in your code anywhere, so you cannot set a prototype property on it. (In jQuery, $.fn is set to jQuery.prototype, that's why you can set $.fn.someMethod.)
If you want the hasClass method to exists on your objects, you need to modify the prototype of query. Your $ function returns new query objects, so query is where the hasClass method should be.
Also, your hasClass method returns an array. Arrays do not have a method called hide. You need to have your hasClass method return a query object, so that you can continue to chain methods.
P.S. Shouldn't a hide method set the style.display to 'none'?
Anyway, your code should look like this:
var $;
(function() {
$ = function(e) {
return new query(e);
};
var query = function(e) {
var e = Array.isArray(e) ? e : document.querySelectorAll(e),
i;
for (i = 0; i < e.length; i++) {
this[i] = e[i];
}
this.length = e.length;
return this;
};
query.prototype = {
hide: function() {
var i;
for (i = 0; i < this.length; i++) {
this[i].style.display = 'none';
}
return this;
},
hasClass: function(klass) {
var e = this,
i;
var t = [];
for (i = 0; i < e.length; i++) {
var k = e[i].className;
var array = k.split(' ');
// If the element has the class, add it for return
if (array.indexOf(klass) > -1) {
t.push(e[i]);
}
}
// Return the list of matched elements
return new query(t);
}
}
}());
window.onload = function() {
$(".element").hasClass("someClass").hide();
}
<p class="someClass element">You can't see me!</p>
(Note: Array.isArray doesn't work in IE < 9.)
If all you want is to query for elements matching a condition and hide it based on element type, id or class name CSS query selectors along with querySelector() or querySelectorAll() api.
For your code sample the same can be rewritten as below
var elements = document.querySelectorAll("element.someClass");
for(var i = 0; i <elements.length; i++) {
elements[i].style.visibility = 'hidden';
}

Binding event listeners multiple times in JavaScript

I'm trying to get the directory list, level by level, using JavaScript.
I have this paths array as input.
var _paths = [];
_paths.push("meta1/meta2/test/home/myself/hi.jpg");
_paths.push("meta1/meta2/test/home/myself/hi1.jpg");
_paths.push("meta1/meta2/test/home/myself/hi2.jpg");
_paths.push("meta1/meta2/test/work/she/100.jpg");
_paths.push("meta1/meta2/test/work/she/110.jpg");
_paths.push("meta1/meta2/test/work/she/120.jpg");
_paths.push("meta1/meta2/test/work/hard/soft/she/120.jpg");
_paths.push("meta1/meta2/test/work/hard/soft/she/121.jpg");
_paths.push("meta1/meta2/test/work/she/220.jpg");
and I want to have a "test" as output, which will be clickable. After click "test", it should be replaced by "home" and "work". After click on "home" - "myself", on "work" - "hard" and "she".
I wrote this:
CodepenCode
and it works only once, only when clicking on "test".
Simply rebind the listeners after the directories have been drawn. You bind them only once, thus they work only once.
Wrap the binding function into a named function:
function bindListeners(){
$('.sub').click(function() {
word = $(this).text();
filteredArr = findString(_paths, word);
drawList(filteredArr, word);
});
}
And call it at the end of drawList:
var drawList = function (paths, word) {
var folders = getFolders(paths, word);
if (folders.length > 0) {
$('.canvas').html('');
for (i = 0; i < folders.length; i++) {
$('.canvas').append("<div class='sub'>" + folders[i] + "</div><br />");
}
}
bindListeners();
}
Demo.
If anyone is curious about building out the data structure:
(function iteratePaths() {
var dirs = [];
for(var i = 0; i < _paths.length; i++) {
buildDirectories(dirs, _paths[i].split('/'));
}
})();
function findDir(dir, obj) {
for(var i = 0; i < dir.length; i++) {
if(dir[i].name === obj.name) {
return dir[i];
}
}
return undefined;
}
function buildDirectories(dir, subs) {
if(subs.length === 0) return;
var obj = {name: subs.shift(), dirs: []};
var existingDir = findDir(dir, obj);
if(!existingDir) {
dir.push(obj);
}
buildDirectories((existingDir || obj).dirs, subs);
}

Javascript dynamic onChange event on select

I have this javascript snippet:
var selectName["id1","id2","id3"];
setOnClickSelect = function (prefix, selectName) {
for(var i=0; i<selectName.length; i++) {
var selId = selectName[i];
alert(selId);
$(selId).onchange = function() {
$(selId).value = $(selId).options[$(selId).selectedIndex].text;
}
}
}
But when I change value to my id1 element, the alert wrote me always "id3".
Can I fix it?
EDIT:
I've changed my snippet with these statements:
setOnChangeSelect = function (prefix, selectName) {
for(var i=0; i<selectName.length; i++) {
var selId = selectName[i];
$(selId).onchange = (function (thisId) {
return function() {
$(selId).value = $(thisId).options[$(thisId).selectedIndex].text;
}
})(selId);
}
}
But selId is always the last element.
This is caused by the behavior of javaScript Closure, selId has been set to the selectName[2] at the end of the loop and that's why you get 'id3' back.
An fix is as following, the key is wrap the callback function inside another function to create another closure.
var selectName = ["id1","id2","id3"];
var setOnClickSelect = function (prefix, selectName) {
for(var i = 0; i < selectName.length; i++) {
var selId = selectName[i];
$(selId).onchange = (function (thisId) {
return function() {
$(thisId).value = $(thisId).options[$(thisId).selectedIndex].text;
}
})(selId);
}
};
Ps: there is synyax error for var selectName["id1","id2","id3"], you should use var selectName = ["id1","id2","id3"];

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