How JavaScript uses hashing
Hashing is taking an input and putting it into a hashing function to and getting an output that basically obscures what the input originally was. Hashing uses a very complicated "one - way" function. This is a function where you cannot take the output and work out exactly what the input was. The only way to see if two things are the same input for example is to put them through the hashing function and compare the 'hashes'
Hash tables are a very clever way of storing data. They can be used to improve a search function from O(n) in a standard linear search or from O(log n) and now make it an algorithm of O(1). You would normally have key value pairs in an object/list of data. You can use hashing to create a number which could be an index in an array. Thus when storing names and phone numbers in a phone book for example, you hash each of the names ( the key ) into a number which would be their index in the phone book array. Then when someone wants to find a persons phone number, the name gets hashed into the number which is the index in the array and the number can be pulled out directly. No search needed.
There is a very important distinction between hashing and encryption. Hashing is not intended to be used to find out what the originaly input was. It is purely to confirm that two inputs are same by comparing their hashes. However, when it comes to encryption, the data that is encrypted does need to be retrieved. So there needs to be a way to decipher what the encrypted data once was. Thus you cannot use a so-called "one way" function to encrypt data.
A Map object holds key-value pairs like a normal object and it remembers the original order of insertion of all of the keys. Any value can be used as either a key or a value within any pair. Maps and objects are similar, both let you set keys to values, retrieve those values, delete keys, and detect whether something is stored at a key. The differences are that Map's don't contain any keys by default but Objects do. Maps only contain what is specifically put into them. A Map's key can be any value but an objects key must be either a string or a symbol. Map entries are iterable and the map object iterates in the order of entry insertion. Maps are better optimized for scenarios involving frequent additions and removals of key-value pairs. Map objects must be implemented using hash tables.