javascript - Why can't I pass "window.location.reload" as an argument to setTimeout?

Question

I would love some insight into the error I am seeing in Safari and Chrome with the following line of code:

setTimeout(window.location.reload, 250);

Chrome reports:
Uncaught TypeError: Illegal invocation

And Safari:
TypeError: Type error

In FireFox, the code runs fine. Also, this code runs fine in each of the three browsers:

setTimeout((function() {
  window.location.reload();
}), 250);

Chrome and Safari have no issues with this code:

var say_hello = function () { alert("hello") };  
setTimeout(say_hello, 250);  

What is special about window.location.reload that causes this error?

(not sure if it's useful or not, but here's a jsfiddle illustrating this)

Answer 1

Because reload() needs window.location as this. In other words - it is a method of window.location. When you say:

var fun = window.location.reload;

fun();

You are calling reload() function without any this reference (or with implicit window reference).

This should work:

setTimeout(window.location.reload.bind(window.location), 250);

The window.location.reload.bind(window.location) part means: take window.location.reload function and return a function that, when called, will use window.location as this reference inside reload().

See also

• How can I pass an argument to a function called using setTimeout?
• Why doesn't console.log work when passed as a parameter to forEach?
• Preserve 'this' reference in javascript prototype event handler