Question 186867 in Javascript Question posted in
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Javascript – Merging a function into an existing object

If one has an existing object obj:

const obj = {
  i: 0,
  foo(){ 
    console.log(this.i) 
    this.i +=1
  }
}

obj.foo() // => 0

Is it possible to merge a function into it:

// the following function code should be added to `obj`
function obj(){
  this.foo()
}

// after the merge the following should both work:
obj.foo() // => 1
obj() // => 2
Tags:

3

Answers


  1. 0

    You can merge function to object using Object.assign. I changed obj() to baz() to make it more clear.

    const obj = {
  i: 0,
  foo() {
    console.log(this.i);
    this.i += 1;
  }
};

function baz() {
  this.foo();
}

Object.assign(obj, { baz });
obj.foo() // => 0
obj.baz() // => 1

    However when you call baz(), it will throw error because it doesn’t understand the context this in baz(). So you need to call baz() with obj as the context

    baz.call(obj); // => 2
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  2. 0

    I am not sure how the obj function is merged into the obj object if you want to call it standalone. However, you could use a bound function instead.

    Besides: You cannot have a constant obj and a function obj that share the same name. I therefor changed the function name to fn:

    const obj = {
  i: 0,
  foo() {
    console.log(this.i);
    this.i += 1;
  }
};

function fn() {
  this.foo();
}



const bound = fn.bind(obj);



bound();
obj.foo();
bound();
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  3. 0

    there are multiple ways to add property to an object like :

    1.using dot notation, 
2.using bracket [ ] notation, 
3.using defineProperty(), 
4.using spread operator, 
5.using Object.assign() 


    const obj = {
  i: 0,
  foo(){ 
    console.log(this.i) 
    this.i +=1
  }
}

const newObj = {...obj, obj(){console.log("ok")}}
newObj.obj()

obj['bar'] = function(){
    console.log("bar")
}

obj.bar()
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