Hash tables are a very practical way to maintain a dictionary. They exploit the fact that looking an item up in an array takes constant time once you have its index. A hash function is a mathematical function that maps keys to integers. We will use the value of our hash function as an index into an array, and store our item at that position. The first step of the hash function is usually to map each key to a big integer. Let α be the size of the alphabet on which a given string S is written. Let char(c) be a function that maps each symbol of the alphabet to a unique integer from 0 to α − 1.
const hash = function(key, arrayLength){
key = +(key.split('').map(a => a.charCodeAt(0) - 96).join(''))
console.log(key);
}