setTimeout passing parameters to a function

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I have a loop in which I want to call a function with setTimeout and pass some arguments.

The function is called 5 times but the argument is not what I expect,in each time the arg1 equals(5).

What I expect is getting arg1= 0 when the function is called for the first time and the second time arg1=1 ending with Arg1 = 4.

What I get is (arg1=5) each time.

JavaScript

foo();
function foo()
{
	for (var i = 0; i < 5; i++)
	{
		setTimeout(
		function(){
		callingByTimeout(i)
		}
		,100)
	}
}
function callingByTimeout(arg1)
{ 
	alert(arg1)
	//output for first time  : 5
	//output for second time : 5
	//output for third time  : 5
	//output for fourth time : 5
	//output for fifth time  : 5
}

thanks in advance.

Regards Jamal

Posted 9-Jan-12 20:08pm

Jamal Seyedi

Updated 28-May-23 22:59pm

Dalek Dave

v3

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Dalek Dave 10-Jan-12 4:09am

Edited for Readability.

3 solutions

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Robby Tendean · Accepted Answer · 2012-01-09T20:50:00

Solution 1

Hi Jamal, why don't you change to code below:

JavaScript

var count = 0;
function foo()
{
  if (count<5)
  {
    alert(count);
    count++;
    var result = setTimeout("foo()",100);
  }
}
foo();

Posted 9-Jan-12 20:50pm

Robby Tendean

Comments

Jamal Seyedi 10-Jan-12 3:17am

thnaks for answring me.
I found the logical way.
We should use clousers in javascript.

Jamal Seyedi 10-Jan-12 3:20am

I mean closures

incaunu · Accepted Answer · 2012-01-09T21:20:00

Solution 2

Hi,

In your example, the callback function of setTimeout is an anonymous function. Because of this, the scope of variable i, is no longer as you expected. When the callback function is invoked, value of i it will be from the foo() function, and in that moment the loop is done and these means the value is 5. You can search on google about these things.

Robby Tendean615 solution is great.

Posted 9-Jan-12 21:20pm

incaunu

Comments

Jamal Seyedi 10-Jan-12 3:27am

thanks, now I found the solution, scope parameters are secret. take a look at solution 3.
I think now I understand what to do.

Jamal Seyedi · Accepted Answer · 2012-01-09T21:21:00

I found the solution.

It works very well:

C#

foo();
function foo(i)
{
    for (var i = 0; i < 5; i++)
    {
        setTimeout(
        function (index)
        {
            return function ()
            {
                callingByTimeout(index);
            }

        } (i)
        , 1000)
    }
}
function callingByTimeout(arg1)
{
    alert(arg1)
    //output for first time  : 0
    //output for second time : 1
    //output for third time  : 2
    //output for fourth time : 3
    //output for fifth time  : 4
}

setTimeout passing parameters to a function

3 solutions

Solution 1

Solution 2

Solution 3

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