javascript OO how to update self parameters with some JSON variable

Question

Lets say I have a javascript object with the the following

var Settings = function () {        
    this.timelimit = 0;
    this.locked    = false;     
    this.expires   = null;      
    this.age       = null;      
};

And then I set some get/set functions like:

Settings.prototype = {

        getAllAges: function () {
            return self.age;
        },

        getTimeLimit: function () {
            return self.timelimit;
        },
        load: function() {
           data_from_local_storage = LoadLocalStorage();
        }
 }

In data_from_local_storage I have JSON variables that match the above variables (timelimit, locked etc .. )

Issue is, the object var settings_ref = Settings() have all these 4 variables - but also have these 3 functions assigned in settings_ref - due to this OO behavior I need to write inside the load() function:

this.timelimit = data_from_local_storage.timelimit
this.age       = data_from_local_storage.age
this.locked    = data_from_local_storage.locked

Because if I'll write this = data_from_local_storage it will destroy my object.

So how can I avoid writing all these variables one-by-one ?

w/o a for loop inside a function
in this example are just 4 but there are much much more and I cannot write it everywhere everytime
I'm looking for some .update() function like in Python or something ..

Any quick shortcut that someone know ?

Place all your options inside an another object literal, eg. this.options = {timelimit:0,...}, and then you can replace the options very simply by doing this.options = data_from_local_storage.. This of course then makes putting options into local storage just as easy.. :) — Keith
– Keith, Commented Oct 17, 2016 at 13:50
@Pointy sorry I wrote a quick code, but I usually write var self = this so that it won't be confuse within other functions there .. — Ricky Levi
– Ricky Levi, Commented Oct 17, 2016 at 13:57

Pointy · Accepted Answer · 2016-10-17 13:46:06Z

2

You can use Object.assign() in ES2015:

    load: function() {
       Object.assign(this, LoadLocalStorage());
    }

It's apparently not supported yet in IE, but there's a polyfill on the MDN page:

if (typeof Object.assign != 'function') {
  (function () {
    Object.assign = function (target) {
      'use strict';
      // We must check against these specific cases.
      if (target === undefined || target === null) {
        throw new TypeError('Cannot convert undefined or null to object');
      }

      var output = Object(target);
      for (var index = 1; index < arguments.length; index++) {
        var source = arguments[index];
        if (source !== undefined && source !== null) {
          for (var nextKey in source) {
            if (source.hasOwnProperty(nextKey)) {
              output[nextKey] = source[nextKey];
            }
          }
        }
      }
      return output;
    };
  })();
}

(Personally I would use Object.defineProperty() to add the method, but that's verbatim from MDN.)

(edit though I guess if you don't have Object.assign() you may not have Object.defineProperty() either :)

answered Oct 17, 2016 at 13:46

Pointy

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1 Comment

Ricky Levi Over a year ago

Object.assign was exactly what I was looking for - thanks !

Keith · Accepted Answer · 2016-10-17 13:59:23Z

1

If you store the data inside another object literal, it makes persisting things to localstorage and back a lot easier.. Here is an example..

//pretend local storage loader
function LoadLocalStorage() {
  return {
      timelimit: 100,
      locked: true,
      expires: new Date(),      
      age:40
  }
}

var Settings = function () {        
    this.data = {
      timelimit: 0,
      locked: false,
      expires: null,      
      age:null
    }
};

Settings.prototype = {
   getAllAges: function () {
     return this.data.age;
   },
   getTimeLimit: function () {
     return this.data.timelimit;
   },
   load: function() {
     this.data = LoadLocalStorage();
   }
}

var settings = new Settings;
console.log('Age before our load');
console.log(settings.getAllAges());
settings.load();
console.log('Age after our load');
console.log(settings.getAllAges());

answered Oct 17, 2016 at 13:59

Keith

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3 Comments

Redu Over a year ago

You might wish to correct as var settings = new Settings();

Keith Over a year ago

@Redu Apparently there optional. stackoverflow.com/questions/3034941/…

Ricky Levi Over a year ago

it's also an option, I just want the this.variable just like any other native object

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