取消选中一个复选框后如何启用所有复选框？ 使用JavaScript

Question

My Code works when I select one checkbox , all gets disabled. Now i want that if i uncheck this selected checkbox, all checkbox should get enabled. Here is what i have tried

<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '80' onclick='return(validate())'>Q- 80. Statute of Liberty is in ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '153' onclick='return(validate())'>Q- 153. Indias Republic day is celebrated on ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '65' onclick='return(validate())'>Q- 65. Popular Language is ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '150' onclick='return(validate())'>Q- 150. Girnar is located at ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '154' onclick='return(validate())'>Q- 154. Largest Waterfall ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '152' onclick='return(validate())'>Q- 152. Asia is an ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '139' onclick='return(validate())'>Q- 139. Diamond is made up of ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '123' onclick='return(validate())'>Q- 123. Largest Desert ? </td> </tr>

JS: This javascript is when one selects the a checkbox , all gets disabled. I want vice versa, that when one deselects the checkbox all should get enabled

function validate(){

            for (i=0; i<document.myForm.check1.length; i++){
                if (document.myForm.check1[i].checked !=true){
                    document.myForm.check1[i].disabled='true';
                }
            }
 }

Answer 1

<script>
    function validate(element){
        for (i=0; i<document.myForm.check1.length; i++){
            if (!(document.myForm.check1[i].checked)){
                document.myForm.check1[i].disabled=true;
            }
            if(!(element.checked)){
                document.myForm.check1[i].disabled=false;
            }
            element.disabled=false;
        }
    }
</script>
<form name="myForm" id="myForm">
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '80' onclick='return(validate(this))'>Q- 80. Statute of Liberty is in ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '153' onclick='return(validate(this))'>Q- 153. Indias Republic day is celebrated on ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '65' onclick='return(validate(this))'>Q- 65. Popular Language is ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '150' onclick='return(validate(this))'>Q- 150. Girnar is located at ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '154' onclick='return(validate(this))'>Q- 154. Largest Waterfall ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '152' onclick='return(validate(this))'>Q- 152. Asia is an ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '139' onclick='return(validate(this))'>Q- 139. Diamond is made up of ? </td> </tr>
<tr> <td colspan='3'> <input type='checkbox' name='check1' value = '123' onclick='return(validate(this))'>Q- 123. Largest Desert ? </td> </tr>
</form>

Try this

In the For loop's First if condition checkes whether each element is checked , It disables the elements which are not checked.

In the second If condition, it checkes whether the clicked element is not checked and enables all elements..

and in the end it enables the clicked element.

Pretty Confusing but serves the purpose...

Answer 2

Several things to be mentioned:

• Once you ckeck the result it is better to leave that single checkbox enabled
• You don't need to add onclick to all checkboxes - it is not efficient, hard to maintain and will produce behind the scenes anonymous functions for each such declaration; You may attach event to parent of all checkboxes and just check the target of the event to filter out all unrelevant elements.

Here is my solution for you:

HTML

<form id="myForm">
  <table>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '80'>Q- 80. Statute of Liberty is in ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '153'>Q- 153. Indias Republic day is celebrated on ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '65'>Q- 65. Popular Language is ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '150'>Q- 150. Girnar is located at ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '154'>Q- 154. Largest Waterfall ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '152'>Q- 152. Asia is an ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '139'>Q- 139. Diamond is made up of ? </td> </tr>
    <tr> <td colspan='3'> <input type='checkbox' name='check1' value = '123'>Q- 123. Largest Desert ? </td> </tr>
  </table>
</form>

JavaScript

function listen(element, event, callback) {
  if(element.attachEvent) { // IE
    element.attachEvent('on'+event, callback);
  } else { // W3C
    element.addEventListener(event, callback);
  }
}

var form = document.querySelector('#myForm');
listen(form, 'click', function(event){
  var checkBoxes, i, checked, target;
  target = event.srcElement || event.target; // IE or W3C 
  if(target.getAttribute('name') === 'check1') {
    checkBoxes = form.querySelectorAll('input[name="check1"]');
    checked = target.checked;
    for(i=0;i<checkBoxes.length;i++) {
      checkBoxes[i].disabled = checked && checkBoxes[i] !== target;
    }
    if(checked) {
      // Validate and do something with result (target.value)
    } else {
      // Reset validation and result
    }
  }
});

Here is a working example: http://jsbin.com/iKiNenA/10/edit

Note: You should place the <script>...</script> after the <form>...</form> in order to be sure that it runs after form DOM is loaded. Otherwise wrap the code with document.onload = funciton() { ... }

With jQuery you can reduce your javascript code just to this:

$(function() {

  $('#myForm').on('click', 'input[name="check1"]', function(event) {
    $('#myForm input[name="check1"]').prop('disabled', event.target.checked);
    event.target.disabled = false;
    if(event.target.checked) {
      // Validate and do something with result (event.target.value)
    } else {
      // Reset validation and result
    }
  });

});

Example: http://jsbin.com/iKiNenA/9/edit

Tested on IE8+, FF, Safari, Chrome (on Mac and Windows)

Answer 3

If you insist to use javascript instead of jQuery as this could be very simple in jQuery, please check here :

http://jsfiddle.net/CYLmn/18/

function validate(thisobj){
        if(thisobj.checked==true){
            for (i=0; i<document.myForm.check1.length; i++){
                if (document.myForm.check1[i].checked !=true){
                    document.myForm.check1[i].disabled='true';
                }
            }
        } else {

            for (i=0; i<document.myForm.check1.length; i++){
                document.myForm.check1[i].disabled='';
            }
        }
 }