A collection of key/value pairs.
Syntax
mapObj = new Map()
Remarks
The keys and values in the collection may be of any type. If you add a value to the collection using an existing key, the new value will replace the old value.
Properties
The following table lists the properties of the Map object.
| Property | Description |
|---|---|
| constructor | Specifies the function that creates a map. |
| prototype | Returns a reference to the prototype for a map. |
| size | Returns the number of elements in a map. |
Methods
The following table lists the methods of the Map object.
| Method | Description |
|---|---|
| clear | Removes all elements from a map. |
| delete | Removes a specified element from a map. |
| forEach | Performs the specified action for each element in a map. |
| get | Returns a specified element from a map. |
| has | Returns true if the map contains a specified element. |
| set | Adds a new element to a map. |
| toString | Returns a string representation of a map. |
| valueOf | Returns the primitive value of the specified object. |
Example
The following example shows how to add members to a Map and then retrieve them.
var m = new Map();
m.set(1, "black");
m.set(2, "red");
m.set("colors", 2);
m.set({x:1}, 3);
m.forEach(function (item, key, mapObj) {
document.write(item.toString() + "<br />");
});
document.write("<br />");
document.write(m.get(2));
// Output:
// black
// red
// 2
// 3
//
// red
Requirements
Supported in the Internet Explorer 11 standards document mode. Also supported in Store apps (Windows 8.1 and Windows Phone 8.1). See Version Information.
Not supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards, Internet Explorer 10 standards. Not supported in Windows 8.