CODEWITHSUNDEEP
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chevestong
chevestong

Reputation: 193

How are these 2 uses of `$this` different?

I'm studying up on some AngularJS code at the moment and I noticed two different uses of $this in the definition of an AngularJS factory:

module.factory('f_sys', function(...) {
  var $this = { data : { id: "123" } };

  ...

  function _updateSystem(d) {
    return $this.data.id == "123";  // (true)
  }

  $this.init = function() {
    ...
  }

  ...

  return $this;
});

What's happening here? Is the init function being added as another key to the var $this object? Is it treated just like another function (i.e. like _updateSystem)?

Upvotes: 0

Views: 36

Answers (1)

trincot
trincot

Reputation: 349908

init is not like the other function. It is like you say: it becomes a property of the $this object. So you can call $this.init(), but to call _updateSystem you cannot write $this._updateSystem(). And as you return $this to the caller, the caller can call init(), but not _updateSystem().

The construction of $this is the same as if you would have written it in one single assignment:

var $this = { 
    data: { 
        id: "123" 
    }, 
    init: function() {
        /* ... */
    }
}

Or in a more modern (ES6) syntax:

const $this = { 
    data: { 
        id: "123" 
    }, 
    init() {
        /* ... */
    }
}

Upvotes: 1

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