Looking for checkbox enable-disable coding techniques: tips to reduce JavaScript code -

i ask encode following restriction in javascript in more optimal way, because way long.

what want mark 2 checkbox options, disabling remaining

<form>   <div>   <input type="checkbox" id="a" name="question1">a) java <br>   <input type="checkbox" id="b" name="question1">b) c <br>   <input type="checkbox" id="c" name="question1">c) c++  <br>   <input type="checkbox" id="d" name="question1">d) c#  <br>   </div> </form>  

and javascript code improve, worked way did, did not like, think it's code.

addeventlistener('load',compruebacheck,false);       function compruebacheck(){         document.getelementbyid('a').onchange = function() {             if (document.getelementbyid('b').checked)              {                 document.getelementbyid('c').disabled = this.checked;                 document.getelementbyid('d').disabled = this.checked;              }             if (document.getelementbyid('c').checked)              {                 document.getelementbyid('b').disabled = this.checked;                 document.getelementbyid('d').disabled = this.checked;              }             if (document.getelementbyid('d').checked)              {                 document.getelementbyid('b').disabled = this.checked;                 document.getelementbyid('c').disabled = this.checked;             }         };         document.getelementbyid('b').onchange = function() {             if (document.getelementbyid('a').checked)              {                 document.getelementbyid('c').disabled = this.checked;                 document.getelementbyid('d').disabled = this.checked;                    }             if (document.getelementbyid('c').checked)              {                 document.getelementbyid('a').disabled = this.checked;                 document.getelementbyid('d').disabled = this.checked;                                }             if (document.getelementbyid('d').checked)              {                 document.getelementbyid('a').disabled = this.checked;                 document.getelementbyid('c').disabled = this.checked;                                }         };         document.getelementbyid('c').onchange = function() {             if (document.getelementbyid('a').checked)              {                 document.getelementbyid('b').disabled = this.checked;                 document.getelementbyid('d').disabled = this.checked;             }             if (document.getelementbyid('b').checked)              {                 document.getelementbyid('a').disabled = this.checked;                 document.getelementbyid('d').disabled = this.checked;             }             if (document.getelementbyid('d').checked)              {                 document.getelementbyid('a').disabled = this.checked;                 document.getelementbyid('b').disabled = this.checked;                        }                        };         document.getelementbyid('d').onchange = function() {             if (document.getelementbyid('a').checked)             {                 document.getelementbyid('b').disabled = this.checked;                 document.getelementbyid('c').disabled = this.checked;             }             if (document.getelementbyid('b').checked)              {                 document.getelementbyid('a').disabled = this.checked;                 document.getelementbyid('c').disabled = this.checked;             }             if (document.getelementbyid('c').checked)              {                 document.getelementbyid('a').disabled = this.checked;                 document.getelementbyid('b').disabled = this.checked;             }         };     } 

sorry inconvenience, i'm starting learn javascript , not think of better technique little experience in language, appreciate alternatives find things can done using javascript. thank you.

i think looking for.
neat question.

addeventlistener('load',compruebacheck,false); function compruebacheck() {   document.getelementbyid('a').onchange = function() { func1(); }   document.getelementbyid('b').onchange = function() { func1(); }   document.getelementbyid('c').onchange = function() { func1(); }   document.getelementbyid('d').onchange = function() { func1(); }   func1();   function func1() {     var count4 =      (document.getelementbyid('a').checked ? 1 : 0) +      (document.getelementbyid('b').checked ? 1 : 0) +      (document.getelementbyid('c').checked ? 1 : 0) +      (document.getelementbyid('d').checked ? 1 : 0);     document.getelementbyid('a').disabled = false;      document.getelementbyid('b').disabled = false;      document.getelementbyid('c').disabled = false;      document.getelementbyid('d').disabled = false;      if (count4 == 2) {       if (!document.getelementbyid('a').checked) { document.getelementbyid('a').disabled = true; }       if (!document.getelementbyid('b').checked) { document.getelementbyid('b').disabled = true; }       if (!document.getelementbyid('c').checked) { document.getelementbyid('c').disabled = true; }       if (!document.getelementbyid('d').checked) { document.getelementbyid('d').disabled = true; }       }     }   }