Collection Types | Lightning Components Developer's Guide

Here are the supported collection type values.

type	Example	Description
`type`[] (Array)	`<aura:attribute name="colorPalette" type="String[]" default="['red', 'green', 'blue']" />`	An array of items of a defined type.
`List`	`<aura:attribute name="colorPalette" type="List" default="['red', 'green', 'blue']" />`	An ordered collection of items.
`Map`	`<aura:attribute name="sectionLabels" type="Map" default="{ a: 'label1', b: 'label2' }" />`	A collection that maps keys to values. A map can’t contain duplicate keys. Each key can map to at most one value. Defaults to an empty object, `{}`. Retrieve values by using `cmp.get("v.sectionLabels")['a']`.
`Set`	`<aura:attribute name="collection" type="Set" default="['red', 'green', 'blue']" />`	A collection that contains no duplicate elements. The order for set items is not guaranteed. For example, `"red,green,blue"` might be returned as `"blue,green,red"`.

Setting List Items

There are several ways to set items in a list. To use a client-side controller, create an attribute of type List and set the items using component.set().

This example retrieves a list of numbers from a client-side controller when a button is clicked.

1<aura:attribute name="numbers" type="List"/>
2<ui:button press="{!c.getNumbers}" label="Display Numbers" />
3<aura:iteration var="num" items="{!v.numbers}">
4  {!num.value}
5</aura:iteration>

1/** Client-side Controller **/
2({
3  getNumbers: function(component, event, helper) {
4    var numbers = [];
5    for (var i = 0; i < 20; i++) {
6      numbers.push({
7        value: i
8      });
9    }
10    component.set("v.numbers", numbers); 
11    }
12})

To retrieve list data from a controller, use aura:iteration.

Setting Map Items

To add a key and value pair to a map, use the syntax myMap['myNewKey'] = myNewValue.

1var myMap = cmp.get("v.sectionLabels");
2 myMap['c'] = 'label3';

The following example retrieves data from a map.

1for (key in myMap){
2     //do something
3}