1.11 Common JavaScript libraries: Map and Set

1.11 Common JavaScript libraries: Map and Set

Map

A Map object holds key-value pairs.

• Use for...ofor forEachcan be traversed in insertion order.
• Key-values ​​can be anything, including functions, objects, or any primitive type.

Commonly used APIs:

• set(key, value): Insert a key-value pair, if the key already exists, the original value will be overwritten
• get(key): Find the keyword, if it does not exist, return undefined
• size: returns the number of key-value pairs
• has(key): returns whether the keyword key is included
• delete(key): delete the keyword key
• clear(): delete all elements

Set

Set objects allow you to store unique values ​​of any type, whether primitive values ​​or object references.

• Use for...ofor forEachcan be traversed in insertion order.

Commonly used APIs:

• add(): add elements
• has(): Returns whether an element is contained
• size: returns the number of elements
• delete(): delete an element
• clear(): delete all elements