javascript - this is undefined inside arrow function - Stack Overflow

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I am trying to access this inside my arrow function:

import myObject from '../myObjectPath';
export const myClass = Fluxxor.createStore({
    initialize() {
        this.list = [];
        this.id = null;
    },
    myOutsideFunction(variable1) {
        // here this in NOT undefined
        myObject.getMyList(this.id, (myList) => {
            // here this in undefined
            this.list = myList;
        } 
    });
)};

But inside arrow function which in ma callback function this is undefined!!

I am using babel to transpile the code:

myOutsideFunction: function myOutsideFunction() {
    var _this = this;
    myObject.getMyList(function (myList) {
        _this.list = myList;
    });
},

I am trying to access this inside my arrow function:

import myObject from '../myObjectPath';
export const myClass = Fluxxor.createStore({
    initialize() {
        this.list = [];
        this.id = null;
    },
    myOutsideFunction(variable1) {
        // here this in NOT undefined
        myObject.getMyList(this.id, (myList) => {
            // here this in undefined
            this.list = myList;
        } 
    });
)};

But inside arrow function which in ma callback function this is undefined!!

I am using babel to transpile the code:

myOutsideFunction: function myOutsideFunction() {
    var _this = this;
    myObject.getMyList(function (myList) {
        _this.list = myList;
    });
},

• javascript
• this
• undefined
• arrow-functions

Share Improve this question Follow edited Aug 16, 2016 at 15:35 Besat asked Aug 16, 2016 at 15:04 BesatBesat 1,4381313 silver badges2929 bronze badges 7

• Bind this, or store it in a temp variable outside the arrow function scope. – Jite Commented Aug 16, 2016 at 15:06
• The value of this depends on how myOutsideFunction is called. How is it called? – Felix Kling Commented Aug 16, 2016 at 15:07
• 1 @Jite the whole idea of using arrow function is to not having to bind this! – Besat Commented Aug 16, 2016 at 15:25
• 1 @ Felix Kling myOutsideFunction is called from another function inside the class. But it shouldn't matter since myOutsideFunction HAS this. – Besat Commented Aug 16, 2016 at 15:26
• 1 @Jite Np :)) Although it does not work for me :D – Besat Commented Aug 16, 2016 at 15:27

 |  Show 2 more ments

1 Answer 1

Sorted by: Reset to default 5

If this is undefined within an arrow function, it's undefined outside of the arrow as well. Arrow function simply capture the this of the surrounding scope.

In this case, you're declaring myOutsideFunction as a method on an object literal and never binding it or doing anything else that would call it with the object as this.

When debugging, bear in mind that transpilers can rename variables (and have to rename this for it to capture correctly). Using the original name in the console without sourcemaps that include renaming will show you undefined even if the original value isn't. Make sure you use the transpiled name in watches or console mands.

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