Difference between map and object

Map Follow object The difference between

	Map	Object
Unexpected key value	Map By default, there are no keys	Object There's a prototype , The key name on the prototype chain may conflict with the setting key name of your own object
Type of key	Map The bond of can be any value , Include functions , Object or any basic type	Object Must be String perhaps Symbol
The order of the keys	Map Of Key Is ordered . So in iterations Map In the order in which the objects are inserted	Object Is chaotic
Size	Map The key value logarithm of can be easily passed through Size Property acquisition	Object The number of key value pairs of can only be calculated manually
iteration	Map yes iterable Of , So it can be iterated directly	iteration Object You need to get its key in some way before you can iterate
performance	It performs better in the scenario of frequent addition and deletion of key value pairs	In the scenario of frequent addition and deletion of key value pairs, no optimization is made

Map The data structure has the following operation methods ：

• size： map.size return Map The total number of members of the structure .
• set(key,value)： Set the key name key Corresponding key value value, Then go back to the whole Map structure , If key There has been a value , Then the key value will be updated , Otherwise, the new key will be generated .（ Because it returns the current Map object , So you can chain call ）
• get(key)： This method reads key Corresponding key value , If you can't find it key, return undefined.
• has(key)： This method returns a Boolean value , Indicates whether a key is currently Map In the object .
• delete(key)： This method deletes a key , return true, If the deletion fails , return false.
• clear()：map.clear() Clear all members , no return value .

Map Structure native provides three ergodic generator functions and one ergodic method

• keys()： Returns the traverser of the key name .
• values()： The traverser that returns the key value .
• entries()： Returns the traverser of all members .
• forEach()： Traverse Map All members of .