Every function returns 10, why?

[omryk78]

function createFunctions() {
    var result = new Array();
 
    for (var i = 0; i < 10; i++) {
        result[i] = function () { return i; };
    }
 
    return result;
}
 

[Dormilich]

Every function returns 10, why?

because of the Closure on line #5.

since JavaScript has function scope, each function block (line #1, #5) has access to its own variables and the variables of any parent scope (function createFunctions() to window, the anonymous function to createFunctions() and window). if a variable from a parent/outer scope is used in the (inner) function, the value is enclosed/retained in the function, even if the function body is left by the parser (and it is used the variable’s value at run-time(!), not at "compile"-time). and since your variable (i) is set to 10 when the outer function is left, the closured variables all have the last value of i (i.e. 10).

to get around that you have to break the closure (often by using an IIFE):

for (var i = 0; i < 10; i++) {
  result.push(
    // this is an IIFE (immediately invoked function expression) 
    function (x) { 
      // a Closure again, but not using loop variable i
      return function() { return x; }
    }(i)
  );
}