changing function once clicked

<script language=javascript>
 
function myFunction(){
/*do something on the first click*/
}
 
function myFunction2(){
/*do something on the second click and any following clicks*/
}
 
var isClicked = 0; //variable to test wheather you clicked the header.
                        //initialy at false
 
function onClickFunction(){
  if(!isClicked){//when you fist click the header isClicked is set to false so it exicutes the first function and sets is clicked to true
    isClicked = 1;
    myFunction();
  }
  else{//any other time you click it, is clicked is set to trues so it exicutes the second function
    myFunction2();
  }
}
 
</script>
 
<h1 class="header" id="myHeader" onclick="onClickFunction()">
header
</h1>