1. Map Of Florida
2. Google Map
3. World Map

MAP

map

Map Of Florida

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map

Map

Mapes

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Google Map

MAP

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World Map

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map

map

map

• Could you show me where it is on the map? (US)
  Can you show me where it is on the map? (UK)
• Could you show me where we are on the map? (US)
  Can you show me where we are on the map? (UK)
• Could you draw me a map with directions? (US)
  Can you draw me a map with directions? (UK)
• Could I have a map of the subway, please? (US)
  Could I have a map of the tube, please? (UK)
• Do you have a map of the subway? (US)
  Do you have a map of the tube? (UK)
• May I have a map? (US)
  Can I have a map? (UK)
• Do you have a map of ...? (US)
  Have you got a map of ...? (UK)

The Map object holds key-value pairs and remembers the original insertion order of the keys. Any value (both objects and primitive values) may be used as either a key or a value.

Syntax

Parameters

iterable

An Array or other iterable object whose elements are key-value pairs (arrays with two elements, e.g. [[ 1, 'one' ],[ 2, 'two' ]]). Each key-value pair is added to the new Map; null values are treated as undefined.

Description

A Map object iterates its elements in insertion order — a for...of loop returns an array of [key, value] for each iteration.

Key equality

Key equality is based on the sameValueZero algorithm: NaN is considered the same as NaN (even though NaN ! NaN) and all other values are considered equal according to the semantics of the operator. In the current ECMAScript specification -0 and +0 are considered equal, although this was not so in earlier drafts. See 'Value equality for -0 and 0' in the Browser compatibility table for details.

Objects and maps compared

Object is similar to Map in that both let you set keys to values, retrieve those values, delete keys, and detect whether something is stored at a key. Because of this (and because there were no built-in alternatives), Objects have been used as Maps historically; however, there are important differences that make using a Map preferable in certain cases:

• The keys of an Object are String and Symbol, whereas they can be any value for a Map, including functions, objects, and any primitive.
• The keys in Map are ordered while keys added to object are not. Thus, when iterating over it, a Map object returns keys in order of insertion. (Note that in the ECMAScript 2015 spec objects do preserve creation order for string and Symbol keys, so traversal of an object with ie only string keys would yield keys in order of insertion)
• You can get the size of a Map easily with the size property, while the number of properties in an Object must be determined manually.
• A Map is an iterable and can thus be directly iterated, whereas iterating over an Object requires obtaining its keys in some fashion and iterating over them.
• An Object has a prototype, so there are default keys in the map that could collide with your keys if you're not careful. As of ES5 this can be bypassed by using Object.create(null), but this is seldom done.
• A Map may perform better in scenarios involving frequent addition and removal of key pairs.

Properties

Map.length

The value of the length property is 0.
To count how many elements are in a Map, use Map.prototype.size.

get Map[@@species]

The constructor function that is used to create derived objects.

Map.prototype

Represents the prototype for the Map constructor. Allows the addition of properties to all Map objects.

Map instances

All Map instances inherit from Map.prototype.

Properties

Map.prototype.constructor

Returns the function that created an instance's prototype. This is the Map function by default.

Map.prototype.size

Returns the number of key/value pairs in the Map object.

Methods

Map.prototype.clear()

Removes all key/value pairs from the Map object.

Map.prototype.delete(key)

Returns true if an element in the Map object existed and has been removed, or false if the element does not exist. Map.prototype.has(key) will return false afterwards.

Map.prototype.entries()

Returns a new Iterator object that contains an array of [key, value] for each element in the Map object in insertion order.

Map.prototype.forEach(callbackFn[, thisArg])

Calls callbackFn once for each key-value pair present in the Map object, in insertion order. If a thisArg parameter is provided to forEach, it will be used as the this value for each callback.

Map.prototype.get(key)

Returns the value associated to the key, or undefined if there is none.

Map.prototype.has(key)

Returns a boolean asserting whether a value has been associated to the key in the Map object or not.

Map.prototype.keys()

Returns a new Iterator object that contains the keys for each element in the Map object in insertion order.

Map.prototype.set(key, value)

Sets the value for the key in the Map object. Returns the Map object.

Map.prototype.values()

Returns a new Iterator object that contains the values for each element in the Map object in insertion order.

Map.prototype[@@iterator]()

Returns a new Iterator object that contains an array of [key, value] for each element in the Map object in insertion order.

Examples

Using the Map object

Using NaN as Map keys

NaN can also be used as a key. Even though every NaN is not equal to itself (NaN ! NaN is true), the following example works because NaNs are indistinguishable from each other:

Iterating Map with for..of

Maps can be iterated using a for..of loop:

Iterating Map with forEach()

Maps can be iterated using the forEach() method:

Relation with Array objects

Cloning and merging Maps

Just like Arrays, Maps can be cloned:

Keep in mind that the data itself is not cloned

Maps can be merged, maintaining key uniqueness:

Maps can be merged with Arrays, too:

Specifications

Browser compatibility

See also