Passing a function as parameter in javascript, undefined error

Question

I have a function which is part of an object called server, i.e server.log is a function which I use to log data. There are other properties of server which I do not want to pass to other functions, though I want server.log to be available to functions in other files.

function test() {
    testingThis(server.log);
}

function testingThis(logf) {
    logf("test123");
}

I get an error saying

Cannot read property 'emit' of undefined

I am using happy console module to log (server.log works fine in test function).

Community · Accepted Answer · 2017-05-23 12:06:09Z

9

Presumably server.log expects this to refer to server. However, the way you call the function, this refers to the global object or undefined (in strict mode).

Bind the function to server:

testingThis(server.log.bind(server));

See also How to access the correct `this` context inside a callback?.

edited May 23, 2017 at 12:06

CommunityBot

11 silver badge

answered Jul 23, 2015 at 20:22

Felix Kling

820k181 gold badges1.1k silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

user1692342 Over a year ago

Yes you are right. Its working now :) Was this pointing to the object of testingThis function ?

vol7ron Over a year ago

I'm not sure how you came across this answer. The question was confusing, ill-defined, and poorly explained. I wouldn't have assumed the value/scope of this to be an issue here, because I did not see this being used at all. The one helpful piece was the emit error message.

Felix Kling Over a year ago

@user1692342: No. As I said, inside logf (server.log) this would refer to the global object or undefined.

Felix Kling Over a year ago

@vol7ron: Just an educated guess from the error message + seeing that log looses its reference to server ... and my crystal ball of course!

Collectives™ on Stack Overflow

Passing a function as parameter in javascript, undefined error

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related