Javascript variables keep track to their copies?

 

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  • What is the most efficient way to deep clone an object in JavaScript? 57 answers
  • Is JavaScript a pass-by-reference or pass-by-value language? 29 answers

    • The get method in the proceeding line returns a reference to the layerIds object within the model: 

    var d = this.model.get('layerIds');

    When the maplayer property on d is set the reference is also manipulated. Basically d and this.model.get('layerIds') will return the same object from memory. 

    d.mapLayer = view.getId();

    If you checked equality between the two you will notice they are the same object.

    d === this.model.get('layerIds') // true

    From Javascript by reference vs. by value:

    "Javascript is always pass by value, but when a variable refers to an object (including arrays), the "value" is a reference to the object." 

    this.model.get('layerIds'); //  returns an object : {mapLayer: null}
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