在setTimeout中使用对象文字函数

Question

im having some code similar to this:

var options = {
    timerInterval: 800,
    timer: null
};

var functions = {
    someFunction: function() {

    }
};

options.timer = setTimeout('functions.someFunction()', options.timerInterval);

This won't fire though, because it can't find the functions object.

What to do? :D

Answer 1

try this:

options.timer = setTimeout(function () {
  functions.someFunction()
}, options.timerInterval)

it's not recommended to write your function argument as a string in a setTimeout b/c it has to do some conversions that adds overhead to your script and can be avoided by using an anonymous function to call your function.

Answer 2

You can do this:

options.timer = setTimeout(functions.someFunction, options.timerInterval);

But... the more robust way to do it is like this:

options.timer = setTimeout(function () {
    functions.someFunction();
}, options.timerInterval);

The second version is better because in JavaScript, the special variable this is dynamically scoped, which means that it will take the value from the scope it is evaluated in, not the scope it was defined in. Do a google search for "understanding javascript this" to find out more.

On a related note, ES5 introduces Function.prototype.bind to deal with this problem.