EDIT 2 (to make the problem more understandable)
The effect I am trying to achieve is the following: everytime an element enters the viewport an 'is-visible' class is added to it and the same 'is-visible' class is removed from the previous element.
Now I've managed to make it work but I run a for loop to remove all is-visible classes before adding the is-visible class to the element in viewport.
It works but in terms of performance I think it would be better to just remove the class from element[i -1]. And this were I can't get it working.
Here is a simplified fiddle were I try to make the element[i-1] solution work: https://jsfiddle.net/epigeyre/vm36fpuo/11/.
EDIT 1 (to answer some of the questions asked)
I have corrected an issue raised by #Catalin Iancu (thanks a lot for your precious help) by using a modulus operator ((i+len-1)%len).
ORIGINAL QUESTION (not really clear)
I am trying to get the previous element in a for loop (to change its class) with following code :
for (var i = 0; i < array.length; i++) {
if(array[i-1] && my other conditions) {
array[i-1].classList.remove('is-visible');
array[i].classList.add('is-visible');
}
}
But it's not removing the class for [i-1] element.
Here is a more complete piece of code of my module (this is running within a scroll eventlistener):
var services = document.getElementsByClassName('services'),
contRect = servicesContainer.getBoundingClientRect();
for (var i = 0; i < services.length; i++) {
var serviceRect = services[i].getBoundingClientRect();
if ( !services[i].classList.contains('active') && Math.round(serviceRect.left) < contRect.right && services[i-1]) {
services[i-1].classList.remove('is-visible');
services[i].classList.add('is-visible');
}
}
Thanks for your help!
Your if(array[i-1] && my other conditions) is always true, except for the very first case where array[-1] doesn't exist. Therefore, it will remove and then add the active class for each element, which will make it seem as only the first element's class has been removed.
What you need is a better if condition or a break statement, when the loop is not needed anymore
for (var i = 0; i < array.length; i++) {
if(array[i] && i != array.length - 1) {
array[i].classList.remove('active');
}
}
array[array.length - 1].classList.add('active');
The problem probably is that based on your code: services[i-1].classList.remove('active'); and services[i].classList.add('active'); the 'active' class you add in current iteration will be removed in next iteration!
So your code has logical errors, array index does not return all prev items!
What if you create a variable that contain the previous element?
var previous = array[0];
for (var i = 0; i < array.length; i++) {
if(previous && my other conditions) {
previous.classList.remove('active');
array[i].classList.add('active');
break;
}
previous = array[i];
}
Related
I want to be able to loop over a few different labels and hide their content based on if a radio button is check or not. This is the solution I came up with, but I keep getting an error in the console.
var hazardOptions = $(".js-hazardous-option");
var hazard = $("input[name=Hazardous]");
for (var i = 0, len = hazard.length; i < len; i++) {
if (hazard[i].id === "HazardousYes" && hazard[i].checked) {
for (var ii = 0, length = hazardOptions.length; ii < length; ii++) {
hazardOptions[ii].show();
}
} else if (hazard[i].id === "HazardousNo" && hazard[i].checked) {
for (var iii = 0, leng = hazardOptions.length; iii < leng; iii++) {
hazardOptions[iii].hide();
}
}
}
The error I get is:
hide() is not a function
Not sure what I'm missing, I've tried having a look online for a similar issue, but with no luck. I'm pretty sure that the problem is here: hazardOptions[iii].hide(); but not really sure why and/or how to fix it.
When you have a list of objects from a JQuery selector, if you try to access them via index you actually get the DOM element back and not the JQuery object. It's confusing for sure but it is in the documentation.
What you effectively need to do is turn it back into a JQuery object:
$(hazardOptions[iii]).hide();
Or you can use the eq() function with does provide the JQuery object ad thus still has the hide() function:
hazardOptions.eq(iii).hide();
Most probably you need to wrap it with $
$(hazardOptions[ii]).hide()
As you currently have it, if hazard.id === "HazardousYes", you are showing all hazardOptions, and if it is "HazardousNo"you are hiding all of them.
You can call .show() and .hide() on a jQuery collection and it will apply that to all elements in the collection. The below code will replicate the logic of your original code, however, the hazardOptions final show/hide state will be solely determined by the last hazard that is checked and has an id equal to "HazardousYes" and "HazardousNo". This may be what you want, but I would imagine it's not.
var hazardOptions = $(".js-hazardous-option");
var hazards = $("input[name=Hazardous]");
hazards.each(function (index, hazard) {
if (hazard.checked) {
if (hazard.id === "HazardousYes") {
hazardOptions.show();
} else if (hazard.id === "HazardousNo") {
hazardOptions.hide();
}
}
}
Edit - Come to think of it, if you don't have elements with duplicate IDs, You can make this really simple:
hazardOptions.show($("#HazardousYes").is(":checked"));
hazardOptions.hide($("#HazardousNo").is(":checked"));
This was given to me as an interview question -- didn't get the job, but I still want to figure it out.
The objective is to write two querySelectorAll functions: one called qsa1 which works for selectors consisting of a single tag name (e.g. div or span) and another called qsa2 which accepts arbitrarily nested tag selectors (such as p span or ol li code).
I got the first one easily enough, but the second one is a bit trickier.
I suspect that, in order to handle a variable number of selectors, the proper solution might be recursive, but I figured I'd try to get something working that is iterative first. Here's what I've got so far:
qsa2 = function(node, selector) {
var selectors = selector.split(" ");
var matches;
var children;
var child;
var parents = node.getElementsByTagName(selectors[0]);
if (parents.length > 0) {
for (var i = 0; i < parents.length; i++) {
children = parents[i].getElementsByTagName(selectors[1]);
if (children.length > 0) {
for (var i = 0; i < parents.length; i++) {
child = children[i];
matches.push(child); // somehow store our result here
}
}
}
}
return matches;
}
The first problem with my code, aside from the fact that it doesn't work, is that it only handles two selectors (but it should be able to clear the first, second, and fourth cases).
The second problem is that I'm having trouble returning the correct result. I know that, just as in qsa1, I should be returning the same result as I'd get by calling the getElementsByTagName() function which "returns a live NodeList of elements with the given tag name". Creating an array and pushing or appending the Nodes to it isn't cutting it.
How do I compose the proper return result?
(For context, the full body of code can be found here)
Here's how I'd do it
function qsa2(selector) {
var next = document;
selector.split(/\s+/g).forEach(function(sel) {
var arr = [];
(Array.isArray(next) ? next : [next]).forEach(function(el) {
arr = arr.concat( [].slice.call(el.getElementsByTagName(sel) ));
});
next = arr;
});
return next;
}
Assume we always start with the document as context, then split the selector on spaces, like you're already doing, and iterate over the tagnames.
On each iteration, just overwrite the outer next variable, and run the loop again.
I've used an array and concat to store the results in the loop.
This is somewhat similar to the code in the question, but it should be noted that you never create an array, in fact the matches variable is undefined, and can't be pushed to.
You have syntax errors here:
if (parents.length > 0) {
for (var i = 0; i < parents.length; i++) {
children = parents[i].getElementsByTagName(selectors[1]);
if (children.length > 0) {
for (var i = 0; i < parents.length; i++) { // <-----------------------
Instead of going over the length of the children, you go over the length of the parent.
As well as the fact that you are reusing iteration variable names! This means the i that's mapped to the length of the parent is overwritten in the child loop!
On a side note, a for loop won't iterate over the elements if it's empty anyway, so your checks are redundant.
It should be the following:
for (var i = 0; i < parents.length; i++) {
children = parents[i].getElementsByTagName(selectors[1]);
for (var k = 0; k < children.length; i++) {
Instead of using an iterative solution, I would suggest using a recursive solution like the following:
var matches = [];
function recursivelySelectChildren(selectors, nodes){
if (selectors.length != 0){
for (var i = 0; i < nodes.length; i++){
recursivelySelectChildren(nodes[i].getElementsByTagName(selectors[0]), selectors.slice(1))
}
} else {
matches.push(nodes);
}
}
function qsa(selector, node){
node = node || document;
recursivelySelectChildren(selector.split(" "), [node]);
return matches;
}
I got a problem to add a onclick event to object who can be many times in same page
I am trying to
var i;
for (i = 1; i<=10; i++) {
var tmpObj='lov_DgId_D_'+i;
var tmpObj2=tmpObj.getElementsByTagName('a')[0];
if (tmpObj2 != null) {
tmpObj2.onclick= DgIdOnClick;
}
}
But got a error TypeError:
Object lov_DgId_D_1 has no method 'getElementsByTagName' , but this is working
lov_DgId_D_2.getElementsByTagName('a')[0].onclick= DgIdOnClick;
This ibject lov_DgId_D_ can be from 1 like lov_DgId_D_1 or lov_DgId_D_99 u.t.c
What wil be the best solution to add onclick to all lov_DgId_D_* objects ?
As you use jquery, the simplest is
for (i = 1; i<=10; i++) {
$('#lov_DgId_D_'+ i+ ' a').click(DgIdOnClick);
}
If you want to bind your event handler to all a elements inside elements whose id starts with lov_DgId_D_, then it's as simple as
$('[id^="lov_DgId_D_"] a').click(DgIdOnClick);
The problem you have is a confusion between the id of an element and the actual element. Some code that should work for you is this one:
var i;
for (i = 1; i<=10; i++) {
var tmpObj=document.getElementById('lov_DgId_D_'+i); // <-- here
var tmpObj2=tmpObj.getElementsByTagName('a')[0];
if (tmpObj2 != null) {
tmpObj2.onclick= DgIdOnClick;
}
}
Slightly easier to read code:
for (var i=0; i<=10; i++) {
var anchor = document.querySelector('#lov_DgId_D_'+i + ' a');
if (anchor) anchor.onclick = DgIdOnClick;
}
A note: this code attaches a click event to the first anchor (a element) inside each element with the id lov_DgId_D_n, with n being 1->10. Your original code seems to want to do the same thing.
Another note: usually when you iterate over elements using their id's to identify them, you are better suited to add a class to those elements instead. It provides for more maintaintable code and probably easier to understand as well.
I'm iterating through a CSS keyframe in order to change the original to a new animation based on the keyframe that is closest the current behavior of the element being animated. I use the function below to obtain the keyframe rules by iterating through the stylesheets.
function findKeyframesRule(rule) {
var ss = document.styleSheets;
for (var i = 0; i < ss.length; ++i) {
for (var j = 0; j < ss[i].cssRules.length; ++j) {
if (ss[i].cssRules[j].type == window.CSSRule.WEBKIT_KEYFRAMES_RULE
&& ss[i].cssRules[j].name == rule) {
return ss[i].cssRules[j];
}
}
}
return null;
}
called like so: var keyframes = findKeyframesRule(anim);
My Problem: I need to get the length/size of ss[i].cssRules[j] (or the variable keyframes because they point to the same WebkitCSSKeyframesRule object) but have been unable to find a way to do so. I found what I think is the source for CSSKeyframesRules here, but it is in C, so I am unable to use the methods they use to find the length/size, i.e. ::length and such.
I know it has a length because I can call things like keyframes[3].keyText and get a value, so it acts like an array.
I have tried keyframes.size(), keyframes.forEach, keyframes.length, and some more attempts but they don't work because it's not an array, it's a CSSKeyframesRule object. I also attempted work arounds using the ¿parent? (I don't what to call it - I mean ss, ss[i], and ss[i].cssRules) including ss[i].cssRules.length which I thought would work but it doesn't.
Here is a fiddle to show my problem
Do any of you have any ideas?
Your code is working fine. Just try to alert
keyframes.cssRules.length
will get 5
alert(keyframes.cssRules.length);
Fiddle: http://jsfiddle.net/creativevilla/T83Nc/
I have some links and want to pass the focus one by one automatically.
I'm using the code below. Works fine passing the focus but only once.
The first time the focus pass, the link change the color, then pass to the next. The one before gets black again and the next is painted red. No problem.
But when its reach the final link doesn't restart.
var i = 0;
var letras = document.getElementsByTagName("a");
function pasaLink() {
if (i == 0) {
letras[letras.length-1].style.color = "black";
} else {
letras[i-1].style.color = "black";
}
letras[i].style.color = "red";
letras[i].focus();
i++;
if (i > letras.length) {
i= 0;
}
setTimeout("pasaLink()",2000);
}
With the final if and i=0; I'm trying to get back to the initial index when reach the final element, and then restart to iterate the entire collection of links in letras.
This function is called in the body.onload().
Any ideas why its not working?
Change your if to:
if (i >= letras.length) {
i= 0;
}
Working example:
http://jsfiddle.net/nivas/Nn62Q/
(click the Orig Button to see the behavior of your code and the New button to see the behavior of the new one. I have added a try...catch to show the error)
Explanation:
Let us say there are five a tags.
You make i = 0 when i > 6 (i.e., 6). But when i becomes 5, letras[i].style.color = "red"; at the beginning of the function fails and an exception is throws a exception. The flow stops here so the if (i > letras.length) will never be reached.
Shouldn't your condition be
if (i == letras.length) {
i= 0;
}
instead?
Once i is equal to the length of your array, reset.