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Detect a button and then press it in JavaScript

I want to make a function that would detect a button on a web page and then click it. But I want it to click a specific item.
function imready()
{
var btn = document.getElementsByClassName('text-xxxs mb-02');
for (var i = 0; i < btn.length; i++)
{
if (btn[i].innerText.indexOf('AK-47') > -1)
{
console.log('runtime');
chrome.runtime.sendMessage({ type: 'dontrun', update: 1 }, function (response) {
});
btn[i].click();
pressok();
}
}
How do I make it so that the var "btn" should equal to document.getElementsbyClassName('x') and also a different className ('y')?

Quoting from https://stackoverflow.com/a/29366682/10450049
getElementsByClassName() returns an HTMLcollection object which is similar to an array but not really an array so you can't call
array methods using the returned value. One hack is to use Array's
prototype methods along with .call()/.apply() to pass the returned
object as the context.
var elems = document.getElementsByClassName("royal") ;
var collapsedElems = document.getElementsByClassName("collapsed");
var earray = Array.prototype.slice.call(elems, 0);
var concatenated = earray.concat.apply(earray, collapsedElems) ;
console.log(concatenated)
Demo Fiddle

As far as i understand your question, you can use document.querySelector('.classX.classY') to select the needed button with both classes.
That works for the case if you only need one button on the page selected, from your code i assume exactly that.

.hide() is not a function error when executing from a loop

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"));

Create a function to get selectors like jquery does with pure javascript

I am tired of including jquery in simple projects but I am so used to using it and I am trying to break free form my dependency on it. I am trying to create a function that will give the same feel of getting selectors like classes and tags. Example: $('selector').innerHTML = ".something";. I have just been looping through them one by one like so:
var classElements = document.querySelectorAll('.something');
for (var i = classElements.length - 1; i >= 0; i--) {
classElements[i].innerHTML = "This Is A Div";
}
But I wanted to create a function where I could just loop through a selector without having to write out a for loop for everything that I want to find. So I could just write it our like above $('.something').innerHTML = "something";
So far this is what I have but it will only get the first of each selector and won't get all of them. Needless to say I am very stuck and the more I read on the subject the more confused I get. I was wondering if someone could point me in the right direction where my thinking is flawed or explain how jquery goes about doing this. Here is my code:
window.getElements = function(selector) {
var selectors = document.querySelectorAll(selector);
for (var i = selectors.length - 1; i >= 0; i--) {
var elements = selectors[i];
}
return elements;
};
getElements(".something").innerHTML = "something";
Here is a fiddle Fiddle

Here is how you would do it. I have done what you have asked which is allow you to use all the native functionality rather than coin wrappers around it. jQuery returns its own api which acts on the selectors. What I have done is create a selector which allows you to act on each element it finds
window.getElements = function(selector,cb) {
var selectors = document.querySelectorAll(selector);
[].forEach.call(selectors, cb);
};
getElements(".something", function(el){el.innerHTML = "ha"});
getElements("#one", function(el){el.style.background = "red" });
It takes the dom list that is found, converts it into an array and then calls your passed function where you pass your native code
Here is a fiddle
https://jsfiddle.net/y52f4wh8/5/
Jquery works differently:
window.jquery = function(selector,cb) {
var selectors = document.querySelectorAll(selector);
function command(cb) {
[].forEach.call(selectors, cb);
};
// Here we return our own api that uses the command function to act on
// our selected list.
return {
html: function(str){
command(function(el){
el.innerHTML=str;
});
},
bg: function(color){
command(function(el){
el.style.background = color;
});
}
}
};
// The jquery way!
jquery(".something").html("ha");

getElements(".something").innerHTML = "something";
this does not work because that your function gets and returns all of the elements, which is a NodeList, but it does not automatically apply methods to every element in the collection as jQuery does. In order to do that, you would have to convert the elements to an array and actually call the function on each element using a loop or some other function.
EDIT: To be clear, you cannot just call NodeList.innerHTML = '' on a NodeList because innerHTML is applied to one element. jQuery internally takes care of BOTH of the collecting of elements, and the applying of methods for you.
EDIT #2: After examining your function more carefully, I have realized there are other issues, but what I wrote above is still the basis from which you want to spring.
You could use something like this for getting elements?:
function getElements(elements) {
return [...querySelectorAll(elements)]
}
But applying functions on nodes is going to be more selective on a case-by-case basis since many of them are applied differently.

The selector part of JQuery is called Sizzle. It has all the functionality that you need but does not come with the other parts of JQuery.
If you would like to find out more about the javascript behind it, I recommend to take a look at the sourcefiles of Sizzle.

jQuery is essentially a wrapper object for NodeList which adds more functionality to DOM operations. If you want to create your own wrapper object which defines functions for bulk versions of all the Element API, you are free to do so, but then you might as well use jQuery or some derivative.
If you want an extremely lightweight proxy object for doing bulk operations on DOM elements, there is the Proxy object in ES6 which can make this very easy to do, but has no IE support.
const $ = function(selector) {
const nodeList = document.querySelectorAll(selector);
return new Proxy(nodeList, {
set: function(target, property, value) {
for (let i = 0; i < target.length; i++) {
target[i][property] = value;
}
},
get: function(target, property) {
return target[0] && target[0][property];
}
});
};
console.log($('p').innerHTML);
$('p').innerHTML = 'Bulk assignement!';
<p>A B C</p>
<p>1 2 3</p>
<p>Do Re Mi</p>

An approach which would be best avoided is to define a setter for innerHTML on NodeList.
Object.defineProperty(NodeList.prototype, 'innerHTML', {
set(text) {
[...this].forEach(elt => elt.innerHTML = text);
}
});
const $ = selector => document.querySelectorAll(selector);
$('.foo').innerHTML = "it works";
<div class="foo"></div>
<div class="foo"></div>

ID Ends With in pure Javascript

I am working in a Javascript library that brings in jQuery for one thing: an "ends with" selector. It looks like this:
$('[id$=foo]')
It will find the elements in which the id ends with "foo".
I am looking to do this without jQuery (straight JavaScript). How might you go about this? I'd also like it to be as efficient as reasonably possible.

Use querySelectorAll, not available in all browsers (like IE 5/6/7/8) though. It basically works like jQuery:
http://jsfiddle.net/BBaFa/2/
console.log(document.querySelectorAll("[id$=foo]"));

You will need to iterate over all elements on the page and then use string functions to test it. The only optimizations I can think of is changing the starting point - i.e. not document.body but some other element where you know your element will be a child of - or you could use document.getElementsByTagName() to get an element list if you know the tag name of the elements.
However, your task would be much easier if you could use some 3rd-party-javascript, e.g. Sizzle (4k minified, the same selector engine jQuery uses).

So, using everything that was said, I put together this code. Assuming my elements are all inputs, then the following code is probably the best I am going to get?
String.prototype.endsWith = function(suffix) {
return this.indexOf(suffix, this.length - suffix.length) !== -1;
};
function getInputsThatEndWith(text) {
var result = new Array();
var inputs = document.getElementsByTagName("input");
for(var i=0; i < inputs.length; i++) {
if(inputs[i].id.endsWith(text))
result.push(inputs[i]);
}
return result;
}
I put it on JsFiddle: http://jsfiddle.net/MF29n/1/

#ThiefMaster touched on how you can do the check, but here's the actual code:
function idEndsWith(str)
{
if (document.querySelectorAll)
{
return document.querySelectorAll('[id$="'+str+'"]');
}
else
{
var all,
elements = [],
i,
len,
regex;
all = document.getElementsByTagName('*');
len = all.length;
regex = new RegExp(str+'$');
for (i = 0; i < len; i++)
{
if (regex.test(all[i].id))
{
elements.push(all[i]);
}
}
return elements;
}
}
This can be enhanced in a number of ways. It currently iterates through the entire dom, but would be more efficient if it had a context:
function idEndsWith(str, context)
{
if (!context)
{
context = document;
}
...CODE... //replace all occurrences of "document" with "context"
}
There is no validation/escaping on the str variable in this function, the assumption is that it'll only receive a string of chars.

Suggested changes to your answer:
RegExp.quote = function(str) {
return str.replace(/([.?*+^$[\]\\(){}-])/g, "\\$1");
}; // from https://stackoverflow.com/questions/494035/#494122
String.prototype.endsWith = function(suffix) {
return !!this.match(new RegExp(RegExp.quote(suffix) + '$'));
};
function getInputsThatEndWith(text) {
var results = [],
inputs = document.getElementsByTagName("input"),
numInputs = inputs.length,
input;
for(var i=0; i < numInputs; i++) {
var input = inputs[i];
if(input.id.endsWith(text)) results.push(input);
}
return results;
}
http://jsfiddle.net/mattball/yJjDV/
Implementing String.endsWith using a regex instead of indexOf() is mostly a matter of preference, but I figured it was worth including for variety. If you aren't concerned about escaping special characters in the suffix, you can remove the RegExp.quote() bit, and just use
new RegExp(suffix + '$').

If you know the type of DOM elements you are targeting,
then get a list of references to them using getElementsByTagName , and then iterate over them.
You can use this optimization to fasten the iterations:
ignore the elements not having id.
target the nearest known parent of elements you want to seek, lets say your element is inside a div with id='myContainer', then you can get a restricted subset using
document.getElementById('myContainer').getElementsByTagName('*') , and then iterate over them.

JS: How do we work with classes in CSS?

How do we manipulate the class of DOM elements with javascript? Is there a getElementsByClassName function?

Standard way is
error_message.className = 'error-message';
But you'll find these functions can simplify things a lot:
function hasClass(ele,cls) {
return ele.className.match(new RegExp('(\\s|^)'+cls+'(\\s|$)'));
}
//chekcs if selected element has class "cls", works for elements with multiple classes
function addClass(ele,cls) {
if (!this.hasClass(ele,cls)) ele.className += " "+cls;
}
//adds new class to element
function removeClass(ele,cls) {
if (hasClass(ele,cls)) {
var reg = new RegExp('(\\s|^)'+cls+'(\\s|$)');
ele.className=ele.className.replace(reg,' ');
}
}
//removes class from element
Usage in a stackoverflow greasemonkey script to show all questions on page, regardless if they're ignored or not:
var childNodes=document.getElementById("questions").childNodes; //array of all questions
for (var i=1; i<childNodes.length; i+=2) //iterates through all questions on page.
{
removeClass(childNodes[i],"tagged-ignored-hidden");
addClass(childNodes[i],"user_defined_class");
}
(Don't worry if the for loop looks weird in that it skips every other element; the specifics of Stackoverflow's DOM layout with extra nodes between questions aren't important here.)
As to document.getElementsByClassName, it returns an array of DOM elements with the specific class (as you would suspect). BUT:
Safari 3.1 has native
getElmentsByClassName support, and
upcoming Firefox 3 and Opera 9.5 will
have it too. It only leaves out,
you’ve guessed it, Internet Explorer.
source

You can change a class in plain-old JavaScript using something like:
document.getElementById('myElement').className = 'myClass';
Or, if you're using JQuery, you can just use the "Class" functions.
Addressing the added details to the question about 'getElementsByClassName' and your comment:
It would probably be safest (and easiest) to use your favourite JavaScript library for this.
JQuery example:
$(".myClassName").each(function() {
//do what you want with the current element $(this)
});
Hope that helps.

Many JavaScript implementations do have a getElementsByClassName method built in. But if they don’t, you can implement it for yourself:
if (typeof Element.prototype.getElementsByClassName == "undefined") {
Element.prototype.getElementsByClassName = function(className) {
var elems = document.getElementsByTagName("*"),
matches = [];
for (var i=0, n=elems.length; i<n; ++i) {
if (elems[i].hasAttribute("class")) {
var classNames = elems[i].getAttribute("class").split(/\s+/);
for (var j=0,m=classNames.length; j<m; ++j) {
if (classNames[j] == className) {
matches.push(elems[i]);
break;
}
}
}
}
return new NodeList(matches);
};
}