Maps

Added in ES 2015.
For key-value pairs that need to be updated frequently the best collection to use is Map.


Advantages over Objects

the key does not have to be a string
browsers are optimised for large maps, not large objects
maps preserve order


const myMap = new Map() 
myMap.set('prop1', 'value1')
myMap.set('prop2', 'value2')

console.log( myMap.get('prop1')

with chaining

const myMap = new Map() 
  .set('prop1', 'value1')
  .set('prop2', 'value2')

with an array

const myMap = new Map() 
  [
    ['prop1', 'value1'],
    ['prop2', 'value2']
]

removing

myMap.delete('prop1');  
myMap.clear(); // removing all

This does not return an array - this returns a MapIterator

myMap.keys()  // { prop1, prop2} 

Adding default properties

const myDefaults = new Map() 
myDefaults.set('prop1','value1')
myDefaults.set('prop2','value2')

const myObject = new Map()
myObject.set('prop2','value2')

const myNewMap = new Map( [...myDefaults, ...myObject] );

map.set( sColChar, false ) => undefined ??




Methods


MethodMutatesDescription
entries  
clear  
delete  
get  
has  
keys  
set  
sort  


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