Checkbox on change event Javascript

Question

In my page I have an array of string and in my script I have a function that excludes the strings that contain certain char.

I control it through 3 check boxes.

I have the functions to do this but my problem is when I check two check boxes one to exclude the strings containing 'a' and one containing 'e'. I get the result of the last checked check box.

How to make a function that will handle all the check boxes and show me the final result.

This is what I have so far :

My html :

<div id="demo"> </div>
<div class="item">
   <form id="aForm"  onchange="filter()">
      <input type="checkbox" id ="A" value="A">Exclude words with 'A'<br>
      <input type="checkbox" id ="E" value="E">Exclude words with 'E'<br>
      <input type="checkbox" id ="O" value="O">Exclude words with 'O'<br>
   <form id="aForm" >
</div> 

<script type="text/javascript">
var animals = ["Bear", "Mouse", "Cat", "Tiger", "Lion"]

function filter () {
    if(document.getElementById('A').checked) {
       var result2 = [];
       for (var animal in Animals) {
          if (Animals[animal].indexOf('a') == -1) {
             result2 += " " + Animals[animal];
          }
          document.getElementById("demo").innerHTML = result2;
        }
     }
    if(document.getElementById('E').checked) {
       var result2 = [];
       for (var animal in Animals) {
           if (Animals[animal].indexOf('e') == -1) {
              result2 += " " + Animals[animal];
            }
            document.getElementById("demo").innerHTML = result2;
        }
     }
    if(document.getElementById('O').checked) {
      var result2 = [];
      for (var animal in Animals)   {
         if (Animals[animal].indexOf('o') == -1) {
            result2 += " " + Animals[animal];
         }
        document.getElementById("demo").innerHTML = result2;
      }
    }
}

the Animals[] array is not getting modified. Code is only setting the innerHTML. Make sure modified Animals[] after the first checkbox is used for the second checkbox. Let me know if you need the working sample. — Raghava Rudrakanth P V
– Raghava Rudrakanth P V, Commented May 12, 2015 at 12:15

Arun P Johny · Accepted Answer · 2015-05-12 12:13:48Z

Because whatever changes was done by the previous checks are overridden by the last if block if it is checked

var animals = ["Bear", "Mouse", "Cat", "Tiger", "Lion"];

function filter() {
  var a = document.getElementById('A').checked,
    e = document.getElementById('E').checked,
    o = document.getElementById('O').checked,
    result2; //make a copy

  result2 = animals.filter(function(value) {
    value = value.toLowerCase();
    return (!a || value.indexOf('a') == -1) && (!e || value.indexOf('e') == -1) && (!o || value.indexOf('o') == -1);
  })
  document.getElementById("demo").innerHTML = result2;
}
filter();

<div id="demo"> </div>
<div class="item">
  <form id="aForm"  onchange="filter()">
    <input type="checkbox" id ="A" value="A"/>Exclude words with 'A'<br/>
    <input type="checkbox" id ="E" value="E"/>Exclude words with 'E'<br/>
    <input type="checkbox" id ="O" value="O"/>Exclude words with 'O'<br/>
  </form>
</div>

S.Krishna · Accepted Answer · 2015-05-13 03:13:29Z

Below logic code should work fine

var Animals = ["Bear", "Mouse", "Cat", "Tiger", "Lion"]

function filter ()
{
var result2 = [];
document.getElementById("demo").innerHTML = "";
for (var animal in Animals)
	{
	//Copy the value to a temp variable which you can manipulate
	thisAnimal = Animals[animal];
	//Check if each check-box is checked and if so, does the value in variable contains the stop-character
	//If it has, blank out the temp variable
	if (document.getElementById('A').checked && thisAnimal.indexOf('a') == -1)
		thisAnimal = "";
	if (document.getElementById('E').checked && thisAnimal.indexOf('e') == -1)
		thisAnimal = "";
	if (document.getElementById('O').checked && thisAnimal.indexOf('o') == -1)
		thisAnimal = "";
	//If the temp variable is not blank, due to one of the above conditions, then append it to the final result
	if(thisAnimal.length > 0)
		result2 += " " + thisAnimal;
	document.getElementById("demo").innerHTML = result2;
	}
}
// Call the function to display the result for the initial run
filter ();

<div id="demo"> </div>
 <div class="item">
<form id="aForm"  onchange="filter()">
    <input type="checkbox" id ="A" value="A">Exclude words with 'A'<br>
    <input type="checkbox" id ="E" value="E">Exclude words with 'E'<br>
    <input type="checkbox" id ="O" value="O">Exclude words with 'O'<br>
</form>
</div>

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