Arrays and objects are two of the main data structures in JavaScript. In the following table they are compared side by side:
| Arrays | Objects |
| Store values | Store key-value pairs |
| Access by index | Access by key |
Constructors
var arr = []; // preferred new Array(); |
Constructors
var obj = {};
new Stack(); // or other data type
|
Access
// access by index arr[13]; // use bracket notation var tmp = 13; // tmp stores index var arr[tmp]; // retrieve value |
Access
// access by key obj.key; // use dot notation obj["key"]; // use bracket notation var tmp = "key"; // tmp stores key obj[tmp]; // retrieve value |
Loop
var arr = [1, 2, 3];
for (var i = 0; i < arr.length; i++) {
var value = arr[i];
console.log(value);
}
|
Loop
var obj = { a: 1, b: 2, c: 3 };
for (var key in obj) {
var value = obj[key];
console.log(key + " " + value);
}
|