Call a Javascript function stored in an object property

Question

How come the code below doesn't work?

var x = {};
x.a = alert;
x.a('asdf'); // TypeError: Illegal invocation

The alert function needs is calling context to be `window` so it can't be called with a different context — adeneo, Feb 24 '15 at 10:52
http://stackoverflow.com/questions/10743596/why-are-certain-function-calls-termed-illegal-invocations-in-javascript — Amir Popovich, Feb 24 '15 at 10:53
Agree on the duplication but I believe my example is clearer, as is the answer easier to read and understand. (I "knew" this q was posted but didn't find it) — LosManos, Feb 24 '15 at 11:11

score 2 · Accepted Answer · answered Feb 24 '15 at 10:51

2

Because the internals of the alert function requires that the value of this be window.

x.a.call(window,'asdf');

… will work.

answered Feb 24 '15 at 10:51

Quentin

2

It looks like `window` can be replaced with `null` too(!) – LosManos Feb 24 '15 at 11:00
Can you explain it more. – Manwal Feb 24 '15 at 11:07
1

`x.a.call(null, 'asdf');` works. – LosManos Feb 24 '15 at 11:12

1 Answers1