Checkbox Check Event Listener

Question

Recently I have been working with the Chrome Plugin API and I am looking to develop a plugin which will make life easier for me for managing a website.

Now what I wish to do is to fire an event when a certain checkbox is checked. As this website does not belong to me I cannot change the code therefore I am using the Chrome API. One of the main problems is that rather than there being an ID, there is a Name. I was wondering if I could fire the function once the certain checkbox with the 'name' is checked.

Answer 1

Short answer: Use the change event. Here's a couple of practical examples. Since I misread the question, I'll include jQuery examples along with plain JavaScript. You're not gaining much, if anything, by using jQuery though.

Single checkbox

Using querySelector.

var checkbox = document.querySelector("input[name=checkbox]");

checkbox.addEventListener('change', function() {
  if (this.checked) {
    console.log("Checkbox is checked..");
  } else {
    console.log("Checkbox is not checked..");
  }
});

<input type="checkbox" name="checkbox" />

Single checkbox with jQuery

$('input[name=checkbox]').change(function() {
  if ($(this).is(':checked')) {
    console.log("Checkbox is checked..")
  } else {
    console.log("Checkbox is not checked..")
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<input type="checkbox" name="checkbox" />

Multiple checkboxes

Here's an example of a list of checkboxes. To select multiple elements we use querySelectorAll instead of querySelector. Then use Array.filter and Array.map to extract checked values.

// Select all checkboxes with the name 'settings' using querySelectorAll.
var checkboxes = document.querySelectorAll("input[type=checkbox][name=settings]");
let enabledSettings = []

/*
For IE11 support, replace arrow functions with normal functions and
use a polyfill for Array.forEach:
https://vanillajstoolkit.com/polyfills/arrayforeach/
*/

// Use Array.forEach to add an event listener to each checkbox.
checkboxes.forEach(function(checkbox) {
  checkbox.addEventListener('change', function() {
    enabledSettings = 
      Array.from(checkboxes) // Convert checkboxes to an array to use filter and map.
      .filter(i => i.checked) // Use Array.filter to remove unchecked checkboxes.
      .map(i => i.value) // Use Array.map to extract only the checkbox values from the array of objects.
      
    console.log(enabledSettings)
  })
});

<label>
   <input type="checkbox" name="settings" value="forcefield">
   Enable forcefield
</label>
<label>
  <input type="checkbox" name="settings" value="invisibilitycloak">
  Enable invisibility cloak
</label>
<label>
  <input type="checkbox" name="settings" value="warpspeed">
  Enable warp speed
</label>

Multiple checkboxes with jQuery

let checkboxes = $("input[type=checkbox][name=settings]")
let enabledSettings = [];

// Attach a change event handler to the checkboxes.
checkboxes.change(function() {
  enabledSettings = checkboxes
    .filter(":checked") // Filter out unchecked boxes.
    .map(function() { // Extract values using jQuery map.
      return this.value;
    }) 
    .get() // Get array.
    
  console.log(enabledSettings);
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<label>
   <input type="checkbox" name="settings" value="forcefield">
   Enable forcefield
</label>
<label>
  <input type="checkbox" name="settings" value="invisibilitycloak">
  Enable invisibility cloak
</label>
<label>
  <input type="checkbox" name="settings" value="warpspeed">
  Enable warp speed
</label>

Answer 2

Since I don't see the jQuery tag in the OP, here is a javascript only option :

document.addEventListener("DOMContentLoaded", function (event) {
    var _selector = document.querySelector('input[name=myCheckbox]');
    _selector.addEventListener('change', function (event) {
        if (_selector.checked) {
            // do something if checked
        } else {
            // do something else otherwise
        }
    });
});

See JSFIDDLE

Answer 3

If you have a checkbox in your html something like:

<input id="conducted" type = "checkbox" name="party" value="0">

and you want to add an EventListener to this checkbox using javascript, in your associated js file, you can do as follows:

checkbox = document.getElementById('conducted');

checkbox.addEventListener('change', e => {

    if(e.target.checked){
        //do something
    }

});