- The keys and values in the map collection may be of any type and if a value is added to the map collection using a key which already exists in the collection, then the new value replaces the old value.
- The iteration of elements in a map object is done in the insertion order and a “for…” loop returns an array of all [key, value] pairs for each iteration.
- The keys used in maps can be any type of values such as functions, objects etc whereas the keys in objects are limited to symbols and strings.
- The size of a map can be known easily by using the size property but while dealing with objects, the size has to be determined manually.
- A Map should be preferred in cases where the requirement involves frequent addition and removal of [key, value] pairs because a map is an iterative data type and can be directly iterated whereas iterating an object requires obtaining its keys in a specific manner.
The Map.entries() method does not require any argument to be passed and returns an iterator object of the map.
Whenever we want to get all the [key, value] pairs of each element of a map using an iterator object, we use the Map.entries() method.
- It does not require any parameters to be passed.
- The Map.entries() method returns the [key, value] pairs of all the elements of a map in the order of their insertion.
Examples of the above function are provided below.
Input : var myMap = new Map(); myMap.set(0, 'geeksforgeeks'); myMap.set(1, 'is an online portal'); myMap.set(2, 'for geeks'); var iterator_obj=myMap.entries(); document.write(iterator_obj.next().value,"<br>"); document.write(iterator_obj.next().value,"<br>"); document.write(iterator_obj.next().value,"<br>"); Output : Array [0, "geeksforgeeks"] Array [1, "is an online portal"] Array [2, "for geeks"]
Explanation: In this example, a map object “myMap” has been created with a three [key, value] pairs and an iterator object “iterator_obj” method is created which uses Map.entries() method to return the [key, value] pairs of all the elements of a map in the order of their insertion.
Array [0, "geeksforgeeks"] Array [1, "is an online portal"] Array [2, "for geeks"]
- If the variable is not of the Map type then the Map.entries() operation throws a TypeError.
- If the “iterator_obj.next().value” is used more number of times as compared to [key, value] pairs of a map, the Map.entries() function returns undefined for all those cases.
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