Consider:
> function hello(what) {
. what = "world";
. return "Hello, " + arguments[0] + "!";
. }
> hello("shazow")
"Hello, world!"
Why does changing the value of what change the value of arguments[0]?
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1 Answer
"Why does changing the value of
whatchange the value ofarguments[0]?"
Because that's how it's designed to work. The formal parameters are directly mapped to the indices of the arguments object.
That is unless you're in strict mode, and your environment supports it. Then updating one doesn't effect the other.
function hello(what) {
"use strict"; // <-- run the code in strict mode
what = "world";
return "Hello, " + arguments[0] + "!";
}
hello("shazow"); // "Hello, shazow!"
8 Comments
David Wolever
Oh… In that case: why is it designed to work that way? And is that design documented anywhere? (not that I don't trust you, of course, I'd just like a bit more detail)
David Wolever
Oh, wait, here we go: "NOTE 1" in 10.6 Arguments Object of ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf
RobG
@DavidWolever—for convenience, there is an HTML version of ES5 on github.
jfriend00
A little lighter reading than the official spec: developer.mozilla.org/en/JavaScript/Reference/…
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