CODEWITHSUNDEEP
javascriptjavascript-objects
Paul Etscheit
Paul Etscheit

Reputation: 513

Accessing an object in JavaScript with argument of function

I want to make a sort of "shopping list" in JS. I'm having trouble accessing the object with the argument of a function. 

shopList = {
  create: function createList(listName) {
    listName = {};
    listName["Banana"] = 2
  },

  output: function output(listName) {
    console.log(listName)
  },

};

shopList.create('list')
shopList.output('list')

When I run shopList.output 'list' is returned. How do I access the object over the argument? Hope this isn't a duplicate, been googling for hours now and didn't make any progress.

Upvotes: 1

Views: 62

Answers (2)

dfsq
dfsq

Reputation: 193261

If you want to be able to configure lists with dynamic names then you need to use bracket notation to create lists within this object. Like this:

var shopList = {
    create: function createList(listName) {
        this[listName] = {};
        this[listName]["Banana"] = 2
    },

    output: function output(listName) {
        return this[listName];
    }
};

shopList.create('list');
console.log(shopList.output('list'));

However, as pointed by @armchairdj in comments, it's better to create a container dedicated property to hold lists:

var shopList = {
    lists: {},

    create: function createList(listName) {
        this.lists[listName] = {};
        this.lists[listName]["Banana"] = 2
    },

    output: function output(listName) {
        return this.lists[listName];
    }
};

Upvotes: 5

armchairdj
armchairdj

Reputation: 1070

If you want to avoid clobbering the methods of your showList object by naively adding arbitrary, user-supplied keys, you should create an internal namespace for your lists.

var shopList = {
  lists:  {},

  create: function (listName) {
    this.lists[listName] = this.lists[listName] || {};

    this.lists[listName].Banana = 2;
  },

  output: function (listName) {
    var list = this.lists[listName];

    if (!list) {
      return console.log('No list named ' + listName + ' found.');
    }

    console.log(list)
  }
};

shopList.create('output');
shopList.output('output');
shopList.create('foo');
shopList.output('foo');
shopList.output('bar');

Upvotes: 2

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