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JavaScript

Posted by Tani Huang
Tani Huang
6,952 Points

Can someone explain more detail, why inside Vue methods, function change it to ()=> will run undefined ?

var book = new Vue ({
  el: '.book-group',
  data: {
    title: 't1',
    author: 'author1',
    summary: 'This is a book',
  },
  methods: {
    sayhello: function() {
      alert(this.title)
    }
  }
})

var book = new Vue ({
  el: '.book-group',
  data: {
    title: 't1',
    author: 'author1',
    summary: 'This is a book',
  },
  methods: {
    sayhello: ()=> {
       alert(this.title)
     }
  }
})

1 Answer

Chris Shaw
Chris Shaw
26,676 Points
Chris Shaw
Chris Shaw
26,676 Points

Hi Tani Huang,

The reason for this is because of how arrow functions behave in ES6 (ECMAScript 2015). Unlike the classic anonymous function syntax, arrow functions use lexical scoping which inherits this from the parent context rather than directly from the current object.

I would recommend you stick with plain old anonymous functions since they will always bind this correctly and are still perfectly valid.

Happy coding!