Why javascript bind doesn't work

Question

function:

function talk(){ 
        console.log(this.name + " dice: ");
}

var Person = function(name, surname){
    this.name = name;
    this.surname = surname;
}

var p = new Person("Mark", "Red");

talk.bind(p);

what's wrong with bind?

Worth adding, for anyone following this question, that you can get "one-time" binding by using a function's `call` or `apply` method. So another solution to the above issue is to replace `.bind` with `.call` (here `talk.call(p)`). — Platinum Azure, Jan 11 '15 at 05:02

score 31 · Accepted Answer · answered Apr 10 '14 at 15:05

31

It does work, talk.bind(p) returns the bound function:

talk.bind(p)();

answered Apr 10 '14 at 15:05

Rob M.

35,491
6
51
50

score 8 · Answer 2 · answered Apr 10 '14 at 15:05

Nothing is wrong with bind()-- it's just not being used correctly. bind() returns a new function which is bound to the object specified. You still need to execute that function:

function talk(){ 
        console.log(this.name + " dice: ");
}

var Person = function(name, surname){
    this.name = name;
    this.surname = surname;
}

var p = new Person("Mark", "Red");

var markTalks = talk.bind(p);

markTalks();    // logs properly

thefourtheye · Answer 3 · 2014-04-10T15:12:19.410

2

There is nothing wrong with bind, it returns a function which is bound to the object passed as argument. So you need to invoke it like this

talk.bind(p)();

edited Apr 10 '14 at 15:12

answered Apr 10 '14 at 15:04

thefourtheye

233,700
52
457
497

score 1 · Answer 4 · answered Apr 10 '14 at 15:15

As mentioned by others, bind appears to work as expected but it needs invoking.

Another solution that is a bit cleaner, especially if each 'Person' object needs the ability to talk, would be to include the function in the person constructor:

var Person = function(name, surname){
    this.name = name;
    this.surname = surname;
    this.talk = function(){
        console.log(this.name + " dice: ");
    }
}

var p = new Person("Mark", "Red");

p.talk();

See this fiddle: http://jsfiddle.net/amspianist/J5BSh/

score 1 · Answer 5 · answered Dec 13 '20 at 04:55

1

call or apply can be used instead of bind

talk.call(p); talk.apply(p);

answered Dec 13 '20 at 04:55

Scott Wager

758
11
9

Why javascript bind doesn't work

5 Answers5