| Method | Description |
|---|
| new Map() | Creates a new Map object |
| set() | Sets the value for a key in a Map |
| get() | Gets the value for a key in a Map |
| clear() | Removes all the elements from a Map |
| delete() | Removes a Map element specified by a key |
| has() | Returns true if a key exists in a Map |
| forEach() | Invokes a callback for each key/value pair in a Map |
| entries() | Returns an iterator object with the [key, value] pairs in a Map |
| keys() | Returns an iterator object with the keys in a Map |
| values() | Returns an iterator object of the values in a Map |
| Property | Description |
|---|
| size | Returns the number of Map elements |
const fruits = new Map([
["apples", 500],
["bananas", 300],
["oranges", 200],
]);
const fruits = new Map();
fruits.set("apples", 500);
fruits.set("bananas", 300);
fruits.set("oranges", 200);
// judge map
fruits instanceof Map;
// List all entries
let text = "";
fruits.forEach(function (value, key) {
text += key + " = " + value;
});
// use object as map key
const apples = { name: "Apples" };
const fruits = new Map();
fruits.set(apples, 500);
| Object | Map |
|---|
| Not directly iterable | Directly iterable |
| Do not have a size property | Have a size property |
| Keys must be Strings (or Symbols) | Keys can be any datatype |
| Keys are not well ordered | Keys are ordered by insertion |
| Have default keys | Do not have default keys |