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Javascript – Setting Events to Unique Anonymous Functions

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Ok, the easiest way to convey my point is with code, so:

function foo(bar){console.log(bar);}
for(var i=1;i<5;i++){
  $('someDiv'+i).onclick=function(){foo(i);};
}

Say you are trying to set the onclick event of an array of elements in your page, and each of these events need to trigger the same function, but passing different parameter, seems simple enough, but if you try to run the code above, all of the click events will print the value 5. The value of i is 5 because the value is incremented with the for loop before it stopped executing, simple enough, but it seems like the anonymous functions that we created refer to the same value as well.

So, well, the first thing that comes to mind is I kind of need to create “instances” of these anonymous functions individually, with the help of this stackoverflow thread, I got to know the answer is self executing anonymous function and a return statement, so here it is:

function foo(bar){
  console.log(bar);
}
for(var i=1;i<5;i++){
  $('someDiv'+i).onclick=function(i){return function(){foo(i);};}(i);
}

This entry is posted in 2012.

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