在页面加载时禁用函数加载

Question

I have some php, javascript and html code. I have a few lines that are identical in 2 functions. When the page loads I just want one of those functions to basically execute and not the other, how can I prevent the other from executing? Example below:

Function 1()
document.getElementById('field1').length=$field1_numrows

Function 2()
document.getElementById('field1').length=$field1_numrows

I don't want the 2nd function to run, right now in the first function there is some code that occurs, so function 2 is actually overwriting function 1's value.

Answer 1

All you need is some sort of a flag. For example:

var wasExecuted;

function runOnce(){
   if( wasExecuted ){
      return;
   }else{
      wasExecuted = true;
      document.getElementById('field1').length=$field1_numrows;
   }
}

runOnce(); //this will run through the 'else' 
runOnce(); //this will exit the runOnce function (as the flag has been set to true)

Answer 2

Is there a reason why you aren't capturing your functions in brackets? Try the below code.

window.onload = function(){
document.getElementById('field1').length=$field1_numrows
};

function 2(){
document.getElementById('field1').length=$field1_numrows
}

Answer 3

What about a flag value? like:

var myFlag = false;
function 1(){
 if(!myFlag){
  document.getElementById('field1').length=$field1_numrows;
  myFlag = true;
 }
}

function 2(){
 if(!myFlag){
  document.getElementById('field1').length=$field1_numrows;
  myFlag = true;
 }
}

Answer 4

Perhaps a more generic solution here :

var already_executed = (function () {
    var done = {};
    return function (tag) {
        var res = done[tag];
        done[tag] = true;
        return res;
        }
    })();    

A tag identifies a group of functions. Only the first of the group will be executed.

You can reuse the same mechanism with different groups of functions by assigning them different tags.

For instance :

function a() {
    if (already_executed("a_or_b")) return;
    console.log ("a is executing");
    // rest of the code
}

function b() {
    if (already_executed("a_or_b")) return;
    console.log ("b is executing");
    // rest of the code
}

function c() {
    if (already_executed("c_or_d")) return;
    console.log ("c is executing");
    // rest of the code
}

function d() {
    if (already_executed("c_or_d")) return;
    console.log ("d is executing");
    // rest of the code
}

Calling

a();
b();
c();
d();

Will result in

a is executing
c is executing

All this being said, I think refactoring your code would be a better investment than relying on such hacks. Keeping wrong code dormant behind such a mechanism is asking for trouble, in my opinion.