How to find out how many times a function is called using javascript / jquery?

Question

Perhaps a strange question, but here it goes: I have a function that I call periodically and inside this function I need to know what iteration I enter, or how many times the function was called. A simplified version of the problem:

jQuery( document ).ready( function(){ setInterval( "myFunction()", 3000 ); }); function myFunction() { alert( "I have been called X times" ); } 

So how can I define X in the above code?

Answer 1

You can simply use a global variable that increments every time you call a function:

 var myFuncCalls = 0; function myFunction() { myFuncCalls++; alert( "I have been called " + myFuncCalls + " times" ); } 

Once your code gets a little more complicated (or if you use many other libraries), you should, however, consider using scope as shown in the other answers here (best explained in one on Vilx ).

Answer 2

Simple version: make a global variable, as in nyarlathotep answer . The problem is if any other code also defines a global variable with the same name, you are both in trouble.

A simple extended version is to give the variable a crazy name that no one will ever use: calledTimesED7E69A7B141457CA8908A612E3D7A3A

Smart version: add this variable to an existing global variable. Remember - the whole object in Javascript!

 $(function(){ setInterval(myFunction, 3000); }); function myFunction() { myFunction.calledTimes++; alert( "I have been called " + myFunction.calledTimes + " times" ); } myFunction.calledTimes = 0; 

Traditional version: use scope to hide this variable.

 $(function() { calledTimes = 0; setInterval(function() { calledTimes++; alert( "I have been called " + calledTimes + " times" ); }, 3000); }); 

This hides "myFunction", so let's try again with a tricky look:

 var myFunction = null; (function() { calledTimes = 0; myFunction = function() { calledTimes++; alert( "I have been called " + calledTimes + " times" ); } })(); $(function () { setInterval(myFunction, 3000); }); 

... and there are two million more ways to hide this variable with scope. Just choose your favorite.

Answer 3

You will need to use closure. Usually you should use a static variable. in Javascript, it will look something like this:

 jQuery( document ).ready( function(){ setInterval( myFunction, 3000 ); }); var myFunction = (function(){ var count = 0; return function(){ count++ alert( "I have been called " + count + " times"); } })(); 

Demo: http://jsfiddle.net/MZQ83/2/

Answer 4

Here is another interesting solution that does not use an external variable. The best part of this is that you can leave any pre-existing functions intact and name them as you normally would. This means that if you try to "connect" to a function in an existing library, this will work just fine for you. It adds an unobtrusive counter and allows you to continue to make normal calls to existing functions; even with arguments!

 // no js library required // pre-existing function var a = function(){ console.log("pre-existing function function"); console.log("arguments:", arguments); }; // add counter func var addFnCounter = function(target){ var swap = target; var count = 0; return function(){ swap.apply(null, arguments); count++; console.log("func has been called " + count + " times"); console.log("\n"); }; }; // usage a = addFnCounter(a); // call a() as you would normally a(); a(1,2,3); a('hello', 'world'); // using your setInterval example setInterval(a, 3000); 

Exit

 pre-existing function function arguments: [] func has been called 1 times pre-existing function function arguments: [1, 2, 3] func has been called 2 times pre-existing function function arguments: ["hello", "world"] func has been called 3 times 

setInterval output

 pre-existing function function arguments: [] func has been called 4 times pre-existing function function arguments: [] func has been called 5 times pre-existing function function arguments: [] func has been called 6 times 

See how it works on jsfiddle

Answer 5

Create a global variable and initialize it with zero. then increment by one when calling the myfunction () function. Display this variable instead of X.

Answer 6

The static variable is clean and it will not pollute your external scale, compared to a closure or decorator, as in other answers.

 var foo = function(){ alert( ++foo.count || (foo.count = 1) ); } // test function callTwice(f){ f(); f(); } callTwice(foo) // will alert 1 then 2 

or

 callTwice( function bar(){ alert( ++bar.count || (bar.count = 1) ); }); // will alert 1 then 2 

the second is an anonymous function. And pay attention to this syntax:

 var foo = function bar(){ /* foo === bar in here */ }