CODEWITHSUNDEEP
javascript
bph
bph

Reputation: 189

Javascript undefined function inside module

Given the following Javascript example:

var obj = function() {
    var _c = function() {
        console.log("c")
    }
    return {
        a: function() {
            b();
        },
        b: function() {
             console.log("b");
        },
        c: function() {
            _c();
        }
    }
}();

calling obj.a() gives an error that b is not defined. This error can be solved by changing b() to this.b(). Can anyone help explain why this is necessary while c can access _c?

Upvotes: 1

Views: 105

Answers (3)

Denny Mathew
Denny Mathew

Reputation: 1132

Need to use this.b because you are returning an object and 'b' in this context is the property of that object. you need to explicitly stated that using this

While _c is a local function defined inside the closure, you can access access it directly in the return object and does not refer to the return object.

Upvotes: 0

Abdul Mannan - Data Engineer
Abdul Mannan - Data Engineer

Reputation: 1092

You should not call b() directly. 

var obj = function() {
  var _c = function() {
      console.log("c")
  }
  return {
      b: function() {
           console.log("b");
      },
      a: function() {
          this.b();
      },
      c: function() {
          _c();
      }
  }
}();
obj.a();

Explanation added :
You are calling b() inside a function where b() is defined on the object. So to call the function b() inside any other function, you should call b with reference to the object like

this.b();

Upvotes: -1

Amadan
Amadan

Reputation: 198436

_c is a local variable that is in scope when _c() is executed. b is not; it is only found on the object itself, so it can be found by this.b.

This confusion is indicative of transplanting object-oriented concepts from other languages to JavaScript. There are no private and public members in JS, and you can't call methods on the same object by leaving the object prefix. There's just local variables (v when var v or let v), global variables (v when no var v or let v) and object properties (obj.prop). A method is object property that contains a function; no more, no less.

Upvotes: 2

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