Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Odd issue with arrow functions and this scope #733

Closed
chrisabrams opened this issue Feb 9, 2015 · 8 comments
Closed

Odd issue with arrow functions and this scope #733

chrisabrams opened this issue Feb 9, 2015 · 8 comments
Labels
outdated A closed issue/PR that is archived due to age. Recommended to make a new issue

Comments

@chrisabrams
Copy link

When using the npm library thinky, I have the following snippet of code:

User.pre('save', (next) => {

    console.log("pre save event\n", this)
    next()

})

Where this will be undefined. However, if I change the arrow function to an ES5 function:

User.pre('save', function(next) {

    console.log("pre save event\n", this)
    next()

})

this is defined as expected. What would cause this to be undefined with an arrow function?
@chrisabrams chrisabrams mentioned this issue Feb 9, 2015
Closed
@developit
Copy link
Member

this is lexically scoped in arrow functions. See #730.

@stefanbruvik
Copy link

https://github.com/nzakas/understandinges6/blob/master/manuscript/02-Functions.md#arrow-functions

@chrisabrams
Copy link
Author

Ah ok...learned something new today :) Thanks @developit and @stebru

@eventualbuddha
Copy link
Member

@sebmck, this is the third or fourth example of this sort of question being raised. Do you think we should put it on the website or docs somewhere?

@dashed
Copy link
Contributor

dashed commented Feb 9, 2015

Yes please.
https://6to5.org/docs/learn-es6/#arrows

First sentence is already misleading:

Arrows are a function shorthand using the => syntax.

@chrisabrams
Copy link
Author

That is exactly how I was mislead. I did not realize that the => behaves similarly to the => in CoffeeScript.

@jamiebuilds
Copy link
Contributor

Open an issue in https://github.com/6to5/6to5.github.io please

@sebmck
Copy link
Contributor

sebmck commented Feb 9, 2015

@eventualbuddha Not sure if there's anything else that can be done since in all the examples where arrow functions are shown they're always presented with an automatic lexical scope binding.

@sebmck sebmck added the invalid label Feb 9, 2015
This was referenced Feb 10, 2015
Closed
Closed
This was referenced Feb 20, 2015
Closed
Closed
@sebmck sebmck mentioned this issue May 11, 2015
Closed
@sebmck sebmck mentioned this issue May 19, 2015
Closed
This was referenced Jun 2, 2015
Closed
Closed
@sebmck sebmck mentioned this issue Jun 20, 2015
Closed
@sebmck sebmck mentioned this issue Aug 1, 2015
Closed
This was referenced Sep 8, 2015
Closed
Closed
@sebmck sebmck mentioned this issue Sep 29, 2015
Closed
@zloirock zloirock mentioned this issue Nov 4, 2015
Closed
@lock lock bot added the outdated A closed issue/PR that is archived due to age. Recommended to make a new issue label Jan 18, 2019
@lock lock bot locked as resolved and limited conversation to collaborators Jan 18, 2019
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Assignees
No one assigned
Labels
outdated A closed issue/PR that is archived due to age. Recommended to make a new issue
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
7 participants
@eventualbuddha @stefanbruvik @developit @dashed @chrisabrams @sebmck @jamiebuilds