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Javascript, Click eventlistener doing the same thing with multiple classes

I'm very new to learning JavaScript, and I've tried to read, and look for similar answers, but everything is pointing at jQuery, which I want to avoid using for this problem. I can't quite work out what is jQuery and what still works in JS...
I have set up a function that can grab the innerHTML but I can't seem to assign it to the same classes, else it'll only work on the first instance, and I tried creating multiple classes but essentially they're all the same button with different values...
document.querySelector(".b1").addEventListener("click", writeDisp);
document.querySelector(".b2").addEventListener("click", writeDisp);
document.querySelector(".b3").addEventListener("click", writeDisp);
document.querySelector(".b4").addEventListener("click", writeDisp);
function writeDisp() {
if(dispNum.length < 9){
if(dispNum === "0") {
dispNum = this.innerHTML
} else {
dispNum = dispNum + this.innerHTML};
document.querySelector(".display").textContent = dispNum;
}
}
}
How can I make this more simple. As there are way more .b* classes to add, and I'd rather not have a massive list if possible.
Thanks,

var class_elem = document.querySelectorAll("button[class^='b']");
function writeDisp(){
if(dispNum.length < 9){
if(dispNum === "0"){dispNum = this.innerHTML}else{dispNum = dispNum + this.innerHTML};
document.querySelector(".display").textContent = dispNum;
}
}
for (var i = 0; i < class_elem.length; i++) {
class_elem[i].addEventListener('click', writeDisp, false);
}
//Here your code in javascript only.

If you don't want to use jquery, you can use native document.querySelectorAll API like this
function writeDisp(){
if(dispNum.length < 9){
if(dispNum === "0"){
dispNum = this.innerHTML
} else {
dispNum = dispNum + this.innerHTML
}
document.querySelector(".display").textContent = dispNum;
}
}
// this line will select all html tags that contains a class
// name starting with 'b'
var doms = document.querySelectorAll("[class^=b]");
doms.forEach(function(dom) {
dom.addEventListener('click', writeDisp);
})
Note
querySelectorAll will fetch only those DOM instance in which b* is defined as first class, so in case of multiple class defintion, it will not fetch those DOMs which don't have the desired classname at first. That means if you have a DOM defintion like <div class="a box"></div>, this will be ignored, as here, classname starting with b sits after a class.

Get JavaScript Object

I am working client side on a web page that I am unable to edit.
I want to use JS to click on a particular button, but it does not have a unique identifier.
I do know the class and I do know a (unique) string in the innerHTML that I can match with, so I am iterating through the (varying number) of buttons with a while loop looking for the string:
var theResult = '';
var buttonNum = 0;
var searchString = '720p';
while (theResult.indexOf(searchString) == -1
{
theResult = eval(\"document.getElementsByClassName('streamButton')[\" + buttonNum + \"].innerHTML\");
buttonNum++;
}
Now I should know the correct position in the array of buttons (buttonNum-1, I think), but how do I reference this? I have tried:
eval(\"document.getElementsByClassName('streamButton')[\" + buttonNum-1 + \"].click()")
and variation on the position of ()'s in the eval, but I can't get it to work.

You could try something like:
var searchStr = '720p',
// Grab all buttons that have the class 'streambutton'.
buttons = Array.prototype.slice.call(document.querySelectorAll('button.streamButton')),
// Filter all the buttons and select the first one that has the sreachStr in its innerHTML.
buttonToClick = buttons.filter(function( button ) {
return button.innerHTML.indexOf(searchStr) !== -1;
})[0];

You don't need the eval, but you can check all the buttons one by one and just click the button immediately when you find it so you don't have to find it again.
It is not as elegant as what #Shilly suggested, but probably more easily understood if you are new to javascript.
var searchString = '720p';
var buttons = document.getElementsByClassName("streamButton"); // find all streamButtons
if(buttons)
{
// Search all streamButtons until you find the right one
for(var i = 0; i < buttons.length; i++)
{
var button = buttons[i];
var buttonInnerHtml = button.innerHTML;
if (buttonInnerHtml.indexOf(searchString) != -1) {
button.click();
break;
}
}
}
function allOtherClick() {
console.log("Wrong button clicked");
}
function correctButtonClick() {
console.log("Right button clicked");
}
<button class='streamButton' onclick='allOtherClick()'>10</button>
<button class='streamButton' onclick='allOtherClick()'>30</button>
<button class='streamButton' onclick='correctButtonClick()'>720p</button>
<button class='streamButton' onclick='allOtherClick()'>abcd</button>

I would stay clear of eval here, what if the text on the button is some malicious javaScript?
Can you use jQuery? if so, check out contains. You can use it like so:
$(".streamButton:contains('720p')")

Dynamic show/hide div with javascript not working

I have a basic show/hide javascript that works, as long as i don't make it dynamic and make sure of a parameter. I would appreciate a lot if anyone could help me figure out why the dynamic version doesn't work.
Working code:
javascript
function togglesDiv(){
var catdiv = document.getElementById("addNewCat");
if(catdiv.style.display == ""){
catdiv.style.display = "none";
} else {
catdiv.style.display = "";
}
}
html
<span onclick="togglesDiv();">Add new category</span>
<div id="addNewCat" style="display: none;">
lalala
</div>
Non working code:
javascript
function togglesDiv(divsId){
var catdiv = document.getElementById("divsId");
if(catdiv.style.display == ""){
catdiv.style.display = "none";
} else {
catdiv.style.display = "";
}
}
html
<span onclick="togglesDiv(addNewCat);">Add new category</span>
<div id="addNewCat" style="display: none;">
lalala
</div>

You have a variable name wrapped in string delimiters, making it a string literal instead of a variable. Change
var catdiv = document.getElementById("divsId");
To
var catdiv = document.getElementById(divsId);
On the flipside, the call to the function needs the quotes in it's argument (because it should be a string), you can use single quotes to avoid confliction:
<span onclick="togglesDiv('addNewCat');">Add new category</span>

Your code is looking for a div with an ID "divsId" change your code to:
function togglesDiv(divsId){
var catdiv = document.getElementById(divsId);
if(catdiv.style.display == ""){
catdiv.style.display = "none";
} else {
catdiv.style.display = "";
}
}

Because you are looking for a div called "divsId" rather than the value in the variable divsId.
Remove the speach marks!

Remove quotes from
var catdiv = document.getElementById("divsId");
should be
var catdiv = document.getElementById(divsId);
And add quotes:
<span onclick="togglesDiv(addNewCat);">Add new category</span>
Should be
<span onclick="togglesDiv('addNewCat');">Add new category</span>

Remove the quotes:
var catdiv = document.getElementById("divsId");
Becomes
var catdiv = document.getElementById(divsId);
You don't have an element with an ID of "divsId".
On a completely unrelated note, you can't be sure that catdiv.style.display will always be equal to "" when it is visibile. There are other styles which cause it to be displayed ('inline', 'block', for example).
A better solution might be:
function togglesDiv(divsId){
var catdiv = document.getElementById("divsId");
if(catdiv.style.display === "none"){
catdiv.style.display = "";
} else {
catdiv.style.display = "none";
}
}
(And yes, I did mean to put the triple equals === in)

Improved function
function toggleDisplay(id){
var el = document.getElementById(id);
if(!el) return true;
// feature detect to support IE versions.
var dis = 'currentStyle' in el ? el.currentStyle.display : el.style.display;
// toggle display
el.style.display = /none/i.test(dis) ? '' : 'none';
// prevent memory leak
el = null;
}
And as mentioned, quotes are needed when writing yucky inline javascript.
<span onclick="toggleDisplay('addNewCat')"> ... etc
Tbh. pick a js toolkit/library and use it over reinventing the wheel yourself and stop writing inline javascript, your life and happiness will improve substantially if you do =P

How to get all elements inside "div" that starts with a known text

I have a div element in an HTML document.
I would like to extract all elements inside this div with id attributes starting with a known string (e.g. "q17_").
How can I achieve this using JavaScript ?
If needed, for simplicity, I can assume that all elements inside the div are of type input or select.

var matches = [];
var searchEles = document.getElementById("myDiv").children;
for(var i = 0; i < searchEles.length; i++) {
if(searchEles[i].tagName == 'SELECT' || searchEles.tagName == 'INPUT') {
if(searchEles[i].id.indexOf('q1_') == 0) {
matches.push(searchEles[i]);
}
}
}
Once again, I strongly suggest jQuery for such tasks:
$("#myDiv :input").hide(); // :input matches all input elements, including selects

Option 1: Likely fastest (but not supported by some browsers if used on Document or SVGElement) :
var elements = document.getElementById('parentContainer').children;
Option 2: Likely slowest :
var elements = document.getElementById('parentContainer').getElementsByTagName('*');
Option 3: Requires change to code (wrap a form instead of a div around it) :
// Since what you're doing looks like it should be in a form...
var elements = document.forms['parentContainer'].elements;
var matches = [];
for (var i = 0; i < elements.length; i++)
if (elements[i].value.indexOf('q17_') == 0)
matches.push(elements[i]);

With modern browsers, this is easy without jQuery:
document.getElementById('yourParentDiv').querySelectorAll('[id^="q17_"]');
The querySelectorAll takes a selector (as per CSS selectors) and uses it to search children of the 'yourParentDiv' element recursively. The selector uses ^= which means "starts with".
Note that all browsers released since June 2009 support this.

Presuming every new branch in your tree is a div, I have implemented this solution with 2 functions:
function fillArray(vector1,vector2){
for (var i = 0; i < vector1.length; i++){
if (vector1[i].id.indexOf('q17_') == 0)
vector2.push(vector1[i]);
if(vector1[i].tagName == 'DIV')
fillArray (document.getElementById(vector1[i].id).children,vector2);
}
}
function selectAllElementsInsideDiv(divId){
var matches = new Array();
var searchEles = document.getElementById(divId).children;
fillArray(searchEles,matches);
return matches;
}
Now presuming your div's id is 'myDiv', all you have to do is create an array element and set its value to the function's return:
var ElementsInsideMyDiv = new Array();
ElementsInsideMyDiv = selectAllElementsInsideDiv('myDiv')
I have tested it and it worked for me. I hope it helps you.

var $list = $('#divname input[id^="q17_"]'); // get all input controls with id q17_
// once you have $list you can do whatever you want
var ControlCnt = $list.length;
// Now loop through list of controls
$list.each( function() {
var id = $(this).prop("id"); // get id
var cbx = '';
if ($(this).is(':checkbox') || $(this).is(':radio')) {
// Need to see if this control is checked
}
else {
// Nope, not a checked control - so do something else
}
});

i have tested a sample and i would like to share this sample and i am sure it's quite help full.
I have done all thing in body, first creating an structure there on click of button you will call a
function selectallelement(); on mouse click which will pass the id of that div about which you want to know the childrens.
I have given alerts here on different level so u can test where r u now in the coding .
<body>
<h1>javascript to count the number of children of given child</h1>
<div id="count">
<span>a</span>
<span>s</span>
<span>d</span>
<span>ff</span>
<div>fsds</div>
<p>fffff</p>
</div>
<button type="button" onclick="selectallelement('count')">click</button>
<p>total element no.</p>
<p id="sho">here</p>
<script>
function selectallelement(divid)
{
alert(divid);
var ele = document.getElementById(divid).children;
var match = new Array();
var i = fillArray(ele,match);
alert(i);
document.getElementById('sho').innerHTML = i;
}
function fillArray(e1,a1)
{
alert("we are here");
for(var i =0;i<e1.length;i++)
{
if(e1[i].id.indexOf('count') == 0)
a1.push(e1[i]);
}
return i;
}
</script>
</body>
USE THIS I AM SURE U WILL GET YOUR ANSWER ...THANKS

Editing all external links with javascript

How can I go through all external links in a div with javascript, adding (or appending) a class and alt-text?
I guess I need to fetch all objects inside the div element, then check if each object is a , and check if the href attributen starts with http(s):// (should then be an external link), then add content to the alt and class attribute (if they don't exist create them, if they do exists; append the wanted values).
But, how do I do this in code?

This one is tested:
<style type="text/css">
.AddedClass
{
background-color: #88FF99;
}
</style>
<script type="text/javascript">
window.onload = function ()
{
var re = /^(https?:\/\/[^\/]+).*$/;
var currentHref = window.location.href.replace(re, '$1');
var reLocal = new RegExp('^' + currentHref.replace(/\./, '\\.'));
var linksDiv = document.getElementById("Links");
if (linksDiv == null) return;
var links = linksDiv.getElementsByTagName("a");
for (var i = 0; i < links.length; i++)
{
var href = links[i].href;
if (href == '' || reLocal.test(href) || !/^http/.test(href))
continue;
if (links[i].className != undefined)
{
links[i].className += ' AddedClass';
}
else
{
links[i].className = 'AddedClass';
}
if (links[i].title != undefined && links[i].title != '')
{
links[i].title += ' (outside link)';
}
else
{
links[i].title = 'Outside link';
}
}
}
</script>
<div id="Links">
<a name="_Links"></a>
FOO
FILE
SomeWhere
SomeWhere 2
SomeWhere 3
ElseWhere 1
ElseWhere 2
ElseWhere 3
BAR
Show/Hide
</div>
If you are on an account on a shared server, like http://big-server.com/~UserName/, you might want to hard-code the URL to go beyond the top level. On the other hand, you might want to alter the RE if you want http://foo.my-server.com and http://bar.my-server.com marked as local.
[UPDATE] Improved robustness after good remarks...
I don't highlight FTP or other protocols, they probably deserve a distinct routine.

I think something like this could be a starting point:
var links = document.getElementsByTagName("a"); //use div object here instead of document
for (var i=0; i<links.length; i++)
{
if (links[i].href.substring(0, 5) == 'https')
{
links[i].setAttribute('title', 'abc');
links[i].setAttribute('class', 'abc');
links[i].setAttribute('className', 'abc');
}
}
you could also loop through all the A elements in the document, and check the parent to see if the div is the one you are looking for

This can be accomplished pretty easily with Jquery. You would add this to the onload:
$("div a[href^='http']").each(function() {
$(this).attr("alt",altText);
var oldClassAttributeValue = $(this).attr("class");
if(!oldClassAttributeValue) {
$(this).attr("class",newClassAttributeValue);
}
});
You could modify this to add text. Class can also be modified using the css function.

My (non-framework) approach would be something along the lines of:
window.onload = function(){
targetDiv = document.getElementById("divName");
linksArray = targetDiv.getElementsByTagName("a");
for(i=0;i=linksArray.length;i++){
thisLink = linksArray[i].href;
if(thisLink.substring(4,0) = "http"){
linksArray[i].className += "yourcontent"; //you said append so +=
linksArray[i].alt += "yourcontent";
}
}
}
This is not tested but I would start like this and debug it from here.