Question

This SO answer makes a call to setTimeout with four arguments.

 setTimeout(self.process1, 0, self, u);

This confuses me. The documentation I’ve seen for setTimeout only uses two arguments, not four.

What do the last two arguments do?

Answer 1

Quoting the documentation on MDN:

Syntax

var timeoutID = window.setTimeout(func, delay, [param1, param2, ...]);

Note that passing additional parameters to the function in the first
syntax does not work in Internet Explorer.