In addition to the explanation, what does the $ mean in javascript? Here is the code:
var ZebraTable = {
bgcolor: '',
classname: '',
stripe: function(el) {
if (!$(el)) return;
var rows = $(el).getElementsByTagName('tr');
for (var i=1,len=rows.length;i<len;i++) {
if (i % 2 == 0) rows[i].className = 'alt';
Event.add(rows[i],'mouseover',function() {
ZebraTable.mouseover(this); });
Event.add(rows[i],'mouseout',function() { ZebraTable.mouseout(this); });
}
},
mouseover: function(row) {
this.bgcolor = row.style.backgroundColor;
this.classname = row.className;
addClassName(row,'over');
},
mouseout: function(row) {
removeClassName(row,'over');
addClassName(row,this.classname);
row.style.backgroundColor = this.bgcolor;
}
}
window.onload = function() {
ZebraTable.stripe('mytable');
}
Here is a link to where I got the code and you can view a demo on the page. It does not appear to be using any framework. I was actually going through a JQuery tutorial that took this code and used JQuery on it to do the table striping. Here is the link:
http://v3.thewatchmakerproject.com/journal/309/stripe-your-tables-the-oo-way
Can someone explain the following
javascript code?
//Shorthand for document.getElementById
function $(id) {
return document.getElementById(id);
}
var ZebraTable = {
bgcolor: '',
classname: '',
stripe: function(el) {
//if the el cannot be found, return
if (!$(el)) return;
//get all the <tr> elements of the table
var rows = $(el).getElementsByTagName('tr');
//for each <tr> element
for (var i=1,len=rows.length;i<len;i++) {
//for every second row, set the className of the <tr> element to 'alt'
if (i % 2 == 0) rows[i].className = 'alt';
//add a mouseOver event to change the row className when rolling over the <tr> element
Event.add(rows[i],'mouseover',function() {
ZebraTable.mouseover(this);
});
//add a mouseOut event to revert the row className when rolling out of the <tr> element
Event.add(rows[i],'mouseout',function() {
ZebraTable.mouseout(this);
});
}
},
//the <tr> mouse over function
mouseover: function(row) {
//save the row's old background color in the ZebraTable.bgcolor variable
this.bgcolor = row.style.backgroundColor;
//save the row's className in the ZebraTable.classname variable
this.classname = row.className;
//add the 'over' class to the className property
//addClassName is some other function that handles this
addClassName(row,'over');
},
mouseout: function(row) {
//remove the 'over' class form the className of the row
removeClassName(row,'over');
//add the previous className that was stored in the ZebraTable.classname variable
addClassName(row,this.classname);
//set the background color back to the value that was stored in the ZebraTable.bgcolor variable
row.style.backgroundColor = this.bgcolor;
}
}
window.onload = function() {
//once the page is loaded, "stripe" the "mytable" element
ZebraTable.stripe('mytable');
}
The $ doesn't mean anything in Javascript, but it's a valid function name and several libraries use it as their all-encompassing function, for example Prototype and jQuery
From the example you linked to:
function $() {
var elements = new Array();
for (var i=0;i<arguments.length;i++) {
var element = arguments[i];
if (typeof element == 'string') element = document.getElementById(element);
if (arguments.length == 1) return element;
elements.push(element);
}
return elements;
}
The $ function is searching for elements by their id attribute.
This function loops through the rows in a table and does two things.
1) sets up alternating row style. if (i % 2 == 0) rows[i].className = 'alt' means every other row has its classname set to alt.
2) Attaches a mouseover and mouseout event to the row so the row changes background color when the user mouses over it.
the $ is a function set up by various javascript frameworks ( such as jquery) that simply calls document.getElementById
The code basically sets alternating table rows to have a different CSS class, and adds a mouseover and mouseout event change to a third css class, highlighting the row under the mouse.
I'm not sure if jQuery, prototype or maybe another third party JS library is referenced, but the dollar sign is used by jQuery as a selector. In this case, the user is testing to see if the object is null.
$ is the so-called "dollar function", used in a number of JavaScript frameworks to find an element and/or "wrap" it so that it can be used with framework functions and classes. I don't recognize the other functions used, so I can't tell you exactly which framework this is using, but my first guess would be Prototype or Dojo. (It certainly isn't jQuery.)
The code creates a ZebraTable "object" in Javascript, which stripes a table row by row in Javascript.
It has a couple of member functions of note:
stripe(el) - you pass in an element el, which is assumed to be a table. It gets all <tr> tags within the table (getElementsByTagName), then loops through them, assigning the class name "alt" to alternating rows. It also adds event handlers for mouse over and mouse out.
mouseover(row) - The "mouse over" event handler for a row, which stores the old class and background colour for the row, then assigns it the class name "over"
mouseout(row) - The reverse of mouseover, restores the old class name and background colour.
The $ is a function which returns an element given either the elements name or the element itself. It returns null if its parameters are invalid (non-existent element, for example)
I believe the framework being used is Prototype, so you can check out their docs for more info
Have a look at the bottom of the article that you have got the code from, you'll see that they say you'll also need prototype's $ function. From article
In your CSS you’ll need to specify a
default style for table rows, plus
tr.alt and tr.over classes. Here’s a
simple demo, which also includes the
other functions you’ll need (an Event
registration object and Prototype’s $
function).
Related
EDIT: I cleaned up the code a bit and narrowed down the problem.
So I'm working on a Wordpress site, and I'm trying to incorporate drop-downs into my menu on mobile, which means I have to use jQuery to assign classes and id's to my already existing elements. I have this code that already works on premade HTML, but fails on dynamically created id's.
Here is the code:
...
var menuCount = 0;
var contentCount = 0;
//find the mobile menu items
var submenus = $('[title="submenu"]');
if (submenus.length && submenus.parent('.fusion-mobile-nav-item')) {
console.log(submenus);
submenus.addClass('dropdown-title').append('<i id="dropdown-angle" class="fa fa-angle-down" aria-hidden="true"></i>');
submenus.each(function() {
$(this).attr("href", "#m" + menuCount++);
})
var content = submenus.parent().find('ul.sub-menu');
content.addClass('dropdown-content');
content.each(function() {
$(this).attr("id", "m" + contentCount++);
})
}
$(document).on('click', '.dropdown-title', function(e) {
var currentAttrValue = $(this).attr('href');
if ($(e.target).is('.d-active') || $(e.target).parent('.dropdown-title').is('.d-active')) {
$(this).removeClass('d-active');
$(currentAttrValue).slideUp(300).removeClass('d-open');
} else {
$('.dropdown-title').removeClass('d-active');
$('.dropdown-content').slideUp(300).removeClass('d-open');
$(this).addClass('d-active');
console.log($(currentAttrValue));
//THIS LINE FAILS
$(currentAttrValue).slideDown(300).addClass('d-open');
}
e.preventDefault();
});
I've registered the elements with the class dropdown-title using $(document).on(...) but I can't figure out what I need to do to register the elements with the custom ID's. I've tried putting the event callback inside the .each functions, I've tried making custom events to trigger, but none of them will get the 2nd to last line of code to trigger. There's no errors in the console, and when I console log the selector I get this:
[ul#m0.sub-menu.dropdown-content, context: document, selector: "#m0"]
0
:
ul#m0.sub-menu.dropdown-content
context
:
document
length
:
1
selector
:
"#m0"
proto
:
Object[0]
So jQuery knows the element is there, I just can't figure out how to register it...or maybe it's something I'm not thinking of, I don't know.
If you are creating your elements dynamically, you should be assigning the .on 'click' after creating those elements. Just declare the 'on click' callback code you posted after adding the ids and classes instead of when the page loads, so it gets attached to the elements with .dropdown-title class.
Check this jsFiddle: https://jsfiddle.net/6zayouxc/
EDIT: Your edited JS code works... There also might be some problem with your HTML or CSS, are you hiding your submenus? Make sure you are not making them transparent.
You're trying to call a function for a attribute, instead of the element. You probably want $(this).slideDown(300).addClass('d-active'); (also then you don't need $(this).addClass('d-active'); before)
Inside submenus.each loop add your callback listener.
As you are adding the class dropdown-title dynamically, it was not available at dom loading time, that is why event listener was not attached with those elemnts.
var menuCount = 0;
var contentCount = 0;
//find the mobile menu items
var submenus = $('[title="submenu"]');
if (submenus.length && submenus.parent('.fusion-mobile-nav-item')) {
console.log(submenus);
submenus.addClass('dropdown-title').append('<i id="dropdown-angle" class="fa fa-angle-down" aria-hidden="true"></i>');
submenus.each(function() {
$(this).attr("href", "#m" + menuCount++);
// add callback here
$(this).click( function(e) {
var currentAttrValue = $(this).attr('href');
if ($(e.target).is('.d-active') || $(e.target).parent('.dropdown-title').is('.d-active')) {
$(this).removeClass('d-active');
$(currentAttrValue).slideUp(300).removeClass('d-open');
} else {
$('.dropdown-title').removeClass('d-active');
$('.dropdown-content').slideUp(300).removeClass('d-open');
$(this).addClass('d-active');
console.log($(currentAttrValue));
$(currentAttrValue).slideDown(300).addClass('d-active');
}
e.preventDefault();
});
})
var content = submenus.parent().find('ul.sub-menu');
content.addClass('dropdown-content');
content.each(function() {
$(this).attr("id", "m" + contentCount++);
})
}
Turns out my problem is that jQuery is adding to both the mobile menu and the desktop menu, where the desktop menu is being loaded first when I search for that ID that's the one that jQuery finds. So it turns out I was completely wrong about my suspicions.
Since I want to use classes instead of id's in these functions(I have three of the same function with different things I want to .append) I am sure I need to put $(this) in those functions somewhere to only trigger only ONE function on button click and not all three of them. but I am not sure because I am a total beginner in jquery/js, so I would appreciate some help.
$(document).ready(function () {
$(".onclick").click(function () {
$('#favorites').append('<div data-role="main"class="ui-content"><div class="ui-grid-b"><div class="ui-block-a">Arrow</div><div class="ui-block-b">More Info</div><div class="ui-block-c">Unfavorite</div></div></div>');
});
});
http://codepen.io/anon/pen/JYxqEw - HTML And the Jquery Code
$('.onclick') selects all the elements with a class of onclick. That means that, whenever something with class="onclick" is clicked, that function will fire.
If you want all of those elements to append that exact HTML to the #favorites element, then you can leave your code as-is.
However, if what you're trying to do is append that html to the clicked element, that is when you'd use $(this) -- that selects the element you clicked with jQuery, then you can append directly to that element ie:
$(document).ready(function () {
$(".onclick").click(function () {
// this will append the HTML to the element that triggered the click event.
$(this).append('<div data-role="main"class="ui-content"><div class="ui-grid-b"><div class="ui-block-a">Arrow</div><div class="ui-block-b">More Info</div><div class="ui-block-c">Unfavorite</div></div></div>');
});
});
EDIT
so to insert the contents of each .onclick into #favorites, you'll need to use the innerHTML value of the DOM node. example fiddle:
http://jsbin.com/qazepubuzu/edit?html,js,output
When you select something with jQuery, you're actually getting back not just the DOM node, but a jQuery object -- this object contains both a reference to the actual DOM node ([0]), as well as a jquery object ([1]).
So to select the DOM node with $(this), you target the node: $(this)[0]. Then you can use .innerHTML() to grab the HTML contents of the node and do as you like.
Final result:
$(function () {
$('.onclick').click(function () {
$('#favorites').append( $(this)[0].innerHTML );
});
});
So the building blocks are not that complex, but I think you're a novice jQuery developer and so you may not be clear on the difference between jQuery and JS yet.
$(selector, context) allows us to create a jQuery collection for a CSS selector which is the child of a current context DOM node, though if you do not specify one there is an automatic one (which is document.body, I think). Various functions iterating over jQuery collections make the particular element available as this within the JavaScript. To get to the strong element from the .onclick element in the HTML fragment you need to travel up in the hierarchy, then to the appropriate element. Then, we can collect the text from the element. We can do this in either JS or jQuery.
To do this with simply jQuery:
// AP style title case, because Chicago is too crazy.
var to_title_case = (function () { // variable scope bracket
var lower_case = /\b(?:a|an|the|and|for|in|so|nor|to|at|of|up|but|on|yet|by|or)\b/i,
first_word = /^(\W*)(\w*)/,
last_word = /(\w*)(\W*)$/;
function capitalize(word) {
return word.slice(0, 1).toUpperCase() + word.slice(1).toLowerCase();
}
function capitalize_mid(word) {
return lower_case.exec(word) ? word.toLowerCase() : capitalize(word);
}
return function to_title_case(str) {
var prefix = first_word.exec(str),
str_minus_prefix = str.slice(prefix[0].length),
suffix = last_word.exec(str_minus_prefix),
center = str_minus_prefix.slice(0, -suffix[0].length);
return prefix[1] + capitalize(prefix[2]) + center.replace(/\w+/g, capitalize_mid)
+ capitalize(suffix[1]) + suffix[2];
};
})();
$(document).ready(function() {
$(".onclick").click(function () {
var text = $(this).parents('.ui-grid-a').find('.ui-block-a').text();
var html = '<div data-role="main"class="ui-content">'
+ '<div class="ui-grid-b"><div class="ui-block-a">'
+ to_title_case(text) + '</div><div class="ui-block-b">More Info</div>'
+ '<div class="ui-block-c">Unfavorite</div></div></div>';
$("#favorites").append(html);
});
});
I have a div that have a few elements that I want to hide, on users request. Those elements have a particular background color. The call of the function is working (it is associated to a checkbox) but it just doesnt do what i want. Actually, it does nothing. This is what I've got:
function toogleDisplay()
{
var kiddos= document.getElementById('external-events').childNodes; //my div
for(i=0; i < kiddos.length; i++)
{
var a=kiddos[i];
if (a.style.backgroundColor=="#A2B5CD")
{
if (a.style.display!="none")
{
a.style.display='none';
}
else
{
a.style.display='block';
}
}
}
}
What am I doing wrong?
An element's background colour is converted to rgb() (or rgba()) format internally.
But that aside, assuming $ is jQuery (you haven't tagged your question so I don't know!) then a is a jQuery object, which does not have a style property. It looks like you just wanted var a = kiddos[i];.
It is more reliable to use a specific class name instead.
You re wrapping your kiddos[i] in a jquery-object $(kiddos[i]) and then try to access the normal properties of a html-dom-objekt.
You have 2 possibilities:
remove the $()
use jquery-access to the properties
a.css('display', none); // or just a.hide();
Additionally you cant check for '#123456' since the color is transformed. Check (#Niet the Dark Absol)s answer for this
I would suggest adding a class to the elements you want to check. Then instead of trying to use background, you can do
$(kiddos[i]).hasClass('myclass')
or for a very efficient way, you can do it in one line of code.
function toogleDisplay()
{
$('.myclass').toggle(); //this will toggle hide/show
}
The divs would look like this
<div class='myclass'>Content</div>
EDIT - to do it without modifying existing html. I also think the rbg color should be rgb(162, 181, 205) if im not mistaken.
You can try something like this. Its based off the following link
Selecting elements with a certain background color
function toogleDisplay()
{
$('div#external-events').filter(function() {
var match = 'rgb(162, 181, 205)'; // should be your color
return ( $(this).css('background-color') == match );
}).toggle()
}
Your jquery selection of a is causing issues. Unwrap the $() from that and you should be fine.
Also you could end up selecting text nodes that wont have a style property. You should check that the style property exists on the node before trying to access background, display, etc.
Use a class instead of a background and check for that instead.
i think you need to see if the 'nodeType' is an element 'a.nodeType == 1' see Node.nodeType then it will work over multiple lines
var kiddos= document.getElementById('external-events').childNodes; //my div
for(i=0; i < kiddos.length; i++)
{
var a=kiddos[i];
if (a.nodeType == 1){ // Check the node type
if (a.style.backgroundColor=="red")
{
if (a.style.display!="none")
{
a.style.display='none';
}
else
{
a.style.display='block';
}
}
}
}
I decided to go for another aproach, using the idea of Kalel Wade. All the elements that may be (or not) hidden, already had a class name, which were the same for all elements, fortunately.
here comes the code
function toogleDisplay()
{
var kiddos = document.getElementsByClassName("external-event ui-draggable");
for (var i = 0, len = kiddos.length; i < len; i++) {
var a=kiddos[i];
if (a.style.backgroundColor==="rgb(162, 181, 205)")
{
if (a.style.display!="none")
{
a.style.display='none';
}
else
{
a.style.display='block';
}
}
}
}
I have assigned data attributes to every grid class, each value is a different number ranging from 1-64.
I want it so that it adds a class 'success' to the grid class with a data-value="1", i can only get it without the specific value. so it finds all data attributes called data value and adds the success class but I cant figure out how to only add it to classes with the data attribute of 1.
function clickSquare() {
$('.grid').click(function(){
if ( $('.grid').data('value'))
{
$(this).addClass("success");
}
else
{
$(this).addClass("error");
}
});
}
<div data-value="1" class="grid pointer">1</div>
also, if i set up an array
var values = ['1', '2']
how could i do it so that the jquery only attaches the class to values with that of the array. hope that made sense!
You need to use this inside the event handler to refer to the clicked grid element. If you use the selector .grid inside the handler it will return the data value of the first grid element in the page instead of current element
$('.grid').click(function () {
if ($(this).data('value') == 1) {
$(this).addClass("success");
} else {
$(this).addClass("error");
}
});
Demo: Fiddle
I am using Safalra's javascript to create a collapsible list. The script works across several browsers with no problem. However, when I apply the javascript to my own list, it fails to act as expected when I use IE (I'm using 7 at the moment). It simply writes the list, without the expand and contract images.
I copied the Safalra's javascript precisely, so I assume the error must be in my own list. This is how I generated my list:
<body onLoad="makeCollapsible(document.getElementById('libguides'));">
<ul id="libguides">
<script type="text/javascript" src="http://api.libguides.com/api_subjects.php?iid=54&more=false&format=js&guides=true&break=li"></script>
</ul>
(Yes, I do close the body tag eventually.) When I run this in IE, it tells me that line 48 is causing the problem, which appears to be:
node.onclick=createToggleFunction(node,list);
Here's the entire function:
function makeCollapsible(listElement){
// removed list item bullets and the sapce they occupy
listElement.style.listStyle='none';
listElement.style.marginLeft='0';
listElement.style.paddingLeft='0';
// loop over all child elements of the list
var child=listElement.firstChild;
while (child!=null){
// only process li elements (and not text elements)
if (child.nodeType==1){
// build a list of child ol and ul elements and hide them
var list=new Array();
var grandchild=child.firstChild;
while (grandchild!=null){
if (grandchild.tagName=='OL' || grandchild.tagName=='UL'){
grandchild.style.display='none';
list.push(grandchild);
}
grandchild=grandchild.nextSibling;
}
// add toggle buttons
var node=document.createElement('img');
node.setAttribute('src',CLOSED_IMAGE);
node.setAttribute('class','collapsibleClosed');
node.onclick=createToggleFunction(node,list);
child.insertBefore(node,child.firstChild);
}
I confess I'm too much of a javascript novice to understand why that particular line of code is causing the error. I looked at some of the other questions here, and was wondering if it might be a problem with setAttribute?
Thanks in advance.
Edited to add:
Here's the code for the createToggleFunction function. The whole of the script is just these two functions (plus declaring variables for the images).
function createToggleFunction(toggleElement,sublistElements){
return function(){
// toggle status of toggle gadget
if (toggleElement.getAttribute('class')=='collapsibleClosed'){
toggleElement.setAttribute('class','collapsibleOpen');
toggleElement.setAttribute('src',OPEN_IMAGE);
}else{
toggleElement.setAttribute('class','collapsibleClosed');
toggleElement.setAttribute('src',CLOSED_IMAGE);
}
// toggle display of sublists
for (var i=0;i<sublistElements.length;i++){
sublistElements[i].style.display=
(sublistElements[i].style.display=='block')?'none':'block';
}
}
}
Edited to add (again):
Per David's suggestion, I changed all instances of setAttribute & getAttribute...but clearly I did something wrong. IE is breaking at the 1st line (which is simply the doctype declaration) and at line 49, which is the same line of code where it was breaking before:
node.onclick=createToggleFunction(node,list);
Here's the first function as written now:
function makeCollapsible(listElement){
// removed list item bullets and the sapce they occupy
listElement.style.listStyle='none';
listElement.style.marginLeft='0';
listElement.style.paddingLeft='0';
// loop over all child elements of the list
var child=listElement.firstChild;
while (child!=null){
// only process li elements (and not text elements)
if (child.nodeType==1){
// build a list of child ol and ul elements and hide them
var list=new Array();
var grandchild=child.firstChild;
while (grandchild!=null){
if (grandchild.tagName=='OL' || grandchild.tagName=='UL'){
grandchild.style.display='none';
list.push(grandchild);
}
grandchild=grandchild.nextSibling;
}
// add toggle buttons
var node=document.createElement('img');
node.src = CLOSED_IMAGE;
node.className = 'collapsibleClosed';
node.onclick=createToggleFunction(node,list);
child.insertBefore(node,child.firstChild);
}
child=child.nextSibling;
}
}
And here's the second function:
function createToggleFunction(toggleElement,sublistElements){
return function(){
// toggle status of toggle gadget
// Use foo.className = 'bar'; instead of foo.setAttribute('class', 'bar');
if (toggleElement.className == 'collapsibleClosed') {
toggleElement.className = 'collapsibleOpen';
toggleElement.src = OPEN_IMAGE;
} else {
toggleElement.className = 'collapsibleClosed';
toggleElement.src = CLOSED_IMAGE;
}
// toggle display of sublists
for (var i=0;i<sublistElements.length;i++){
sublistElements[i].style.display=
(sublistElements[i].style.display=='block')?'none':'block';
}
}
}
Internet Explorer (until version 8, and then only in best standards mode) has a very broken implementation of setAttribute and getAttribute.
It effectively looks something like this:
function setAttribute(attribute, value) {
this[attribute] = value;
function getAttribute(attribute, value) {
return this[attribute];
}
This works fine iif the attribute name matches the property name, and the property takes a string value.
This isn't the case for the class attribute, where the matching property is className.
Use foo.className = 'bar'; instead of foo.setAttribute('class', 'bar');
node.onclick=createToggleFunction(node,list);
That is probably not what you want. Does createToggleFunction return a function? If it doesn't, then I bet you meant this:
node.onClick = function() { createToggleFunction(node, list); };
If my guess is right then the way you have it will set the onClick event handler to be the result of createToggleFunction, not a function like it needs to be.