remove index and object values from javascript array

Question

I understand that doing a normal array in javascript can i push and remove by doing this:

var array = ["a", "b", "c"];
var id = $(this).attr("id");
var index = $.inArray(id, array);
if(index === -1){
 array.push(id);
}else{
 array.splice(index, 1);
}

but what if i have an array with objects, i can push new items, but how to remove it?:

var array = ["a", Object{ qty="1" }, 
 "b", Object{ qty="1" }, 
 "c", Object{ qty="2" } ];
var id = $(this).attr("id");
var qty = $('#item_'+id).val();
var index = $.inArray(id, array);
if(index === -1){
 array.push(id, {'qty' : qty});
}else{
 array.splice(index, 1);
}

• War10ck: Apologies, but your question is a little unclear. In your second example with the objects, is that array suppose to contain 6 items, 3 letters and 3 objects or are you intending it to be more like a key-value pair where each letter is a key that corresponds to an accompanying object?
• ndAR: Maybe i write incorrectly the array, bat each a, b and c need to coordinate with each object. Thx
• T.J. Crowder: Are the letters unique? Or can "a" appear more than once?
• Felix Kling: I guess you want array.splice(index, 2);, though using an object instead of an array might be even better.
• ndAR: Sorry for the delay, yes, the key a b c .. are unique, so each key will contain object data, or maybe it can be a multidimensional array, but i cannot understand very well the structure.

Answer 1

Assuming that "a", "b", and such can appear only once, you may not want an array at all, but rather some kind of "map" or "dictionary." In ES5 and earlier, it was common to use objects as maps; in ES2015 (aka ES6) and alter, Map is probably the new way to do it.

Since ES2015 is so new, here's the ES5 and earlier approach:

var map = {
 "a": {qty: 1},
 "b": {qty: 1},
 "c": {qty: 2}
];

Each property, a, b, and c maps to an object with a property qty. (Presumably qty isn't the only property those objects will have; if it is, it would probably make more sense to use the value directly rather than wrapping it in an object.)

To add to this, you simply do assignment (rather than push) using the name of the new property, using either dot notation and a literal (unlikely, in your scenario I think) or brackets notation and a string (more likely):

var name = "d";
map[name] = {qty: 1};

To remove, you use the delete keyword rather than splice:

delete map[name];

Accessing is also via map[name]:

var name = "c";
var entry = map[name];
console.log(entry.qty); // 2

---

I mentioned ES2015's Map (MDN reference) above, so:

Creating:

var map = new Map();
map.set("a", {qty: 1});
map.set("b", {qty: 1});
map.set("c", {qty: 2});

or pass in an array of arrays, where the inner arrays have two entries: Name and value:

var map = new Map([
 ["a", {qty: 1}],
 ["b", {qty: 1}],
 ["c", {qty: 2}]
]);

You've already seen above how to add/update an entry:

var name = "d";
map.set(name, {qty: 1});

Removing:

var name = "b";
map.delete(name, {qty: 1});

Getting an entry:

var name = "c";
var entry = map.get(name);
console.log(entry.qty); // 2

Some advantages to Map:

1. The key can be anything, not just a string.

2. You don't have to worry about collision with property names from the prototype such as toString.

3. There's a "weak" variety that only weakly references its keys, meaning you can use keys that may get garbage collected even though they're in the map.

• ndAR: Ok, until here we are going fine, but what if i want to post all data array stored in the Map() ? how can i extract and send it as array? with the simple key now im sending it as array normally.
• T.J. Crowder: @ndAR: If you're using an object, you'd use Object.keys(yourObject) to get an array of its property names (keys). If using a Map, you'd use yourMap.keys().
• ndAR: I think im out of this solution, i cannot understand where do you want to go, what i need is just to pass a simple array to an multidimensional but i don't know how to delete the objects based on key, i can push it, but can;t delete because i don;t know how, with Map() i never worked so is because im asking how to retrieve all items including keys and pass to an ajx post as array data
• ndAR: Well i readed the entire documentation and i figured it out, now i have a small issue, on Chrome it return Uncaught SyntaxError: Unexpected token [ for for(var [key, value] of map.entries()){} is this supported by chrome? if not how can i substitute this for loop ? Thanks
• ndAR: Solved with: myMap.forEach(function(value, key) { console.log(key + " = " + value); }, myMap); Thanks a lot !