Events with native vs. lambda functions [duplicate]

Question

Rather a technical question concerning JavaScript events:

Why does

window.onmousewheel = console.log;

throw an Uncaught TypeError: Illegal invocation, while

window.onmousewheel = function (e) {console.log(e); };

works just as expected and prints the event as string? Why is the console.log, when assigned to window.onmousewheel, not just called with one parameter like the lambda expression?

Chrome doesn't recognize console.log... ... stackoverflow.com/questions/8904782/… ... stackoverflow.com/questions/16615781/… ... stackoverflow.com/questions/12944987/… ... stackoverflow.com/questions/5133649/alias-to-chrome-console-log ... stackoverflow.com/questions/5456709/… — user2437417
– user2437417, Commented Jul 29, 2013 at 17:38
This is more of a question about why foo.bar() is different to fn = foo.bar; fn(). — Paul S.
– Paul S., Commented Jul 29, 2013 at 17:41

Esailija · Accepted Answer · 2013-07-29 17:48:59Z

When function is called without explicit receiver, the receiver is window (or more generally the global object) or undefined depending on strictness. The function referenced by console.log requires that its this value is an instance of Console.

It is not usually done in user code but you could protect your methods from generic calls as well:

MyClass.prototype.method = function() { if( !( this instanceof MyClass ) ) { throw new Error("Invalid invocation"); } };

Naftali · Accepted Answer · 2013-07-29 17:41:54Z

It all has to do with the scope of console.log

You should do:

window.onmousewheel = console.log.bind(console);

Collectives™ on Stack Overflow

Events with native vs. lambda functions [duplicate]

2 Answers 2

1 Comment

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Linked

Related