Global variable is logged as undefined when passed as parameter to setTimeout callback function

Question

I have some JS code as below:

var x = self.someAJAXResponseJSON; // x has some object value here.

setTimeout(function(x){
  console.log("In setTimeout:", x); // But x is undefined here
}, 1000);

So I want to pass x to the setTimeout callback function. But I am getting x as undefined inside the setTimeout.

What am I doing wrong?

Any idea how to fix a similar issue using Dojo.js?

setTimeout(dojo.hitch(this, function(){
  this.executeSomeFunction(x); // What should this be?
  console.log("In setTimeout:", x); // But x is undefined here
}), 1000);

Answer 1

Alternatively you can do it without creating a closure.

function myFunction(str1, str2) {
  alert(str1); //hello
  alert(str2); //world
}

window.setTimeout(myFunction, 10, 'hello', 'world');

But note it doesn't work on IE < 10 according to MDN.

Answer 2

When setTimeout invokes the callback, it doesn't pass any arguments (by default); that is, the argument x is undefined when the callback is invoked.

If you remove the parameter x, x in the function body won't refer to the undefined parameter but instead to the variable you defined outside the call to setTimeout().

var x = "hello";
setTimeout(function () { //note: no 'x' parameter
    console.log("setTimeout ... : " + x);
}, 1000);

Alternatively, if it must be a parameter, you can pass it as an argument to setTimeout (do yourself a favor and name it differently, though):

var x = "hello";
setTimeout(function (y) {
    console.log("setTimeout ... : " + y);
}, 1000, x);

Answer 3

Ran into this myself and looked at the Node docs, arguments to be passed into the function come in as a 3rd(or more) parameter to the setTimeout call so...

myfunc = function(x){console.log(x)};
x = "test";
setTimeout(myfunc,100,x);

Worked for me.