function hashStringToInt(s, tableSize) {
    let hash = 17;

    for (let i = 0; i < s.length; i++) {
        hash = (13 * hash * s.charCodeAt(i)) % tableSize
    }

    return hash;
}

class HashTable {
    table = new Array(3)
    numItems = 0;

    resize = () => {
        const newTable = new Array(this.table.length * 2);
        this.table.forEach(item => {
            if (item) {
                item.forEach(([key, value]) => {
                    const idx = hashStringToInt(key, newTable.length);
                    if (newTable[idx]) {
                        newTable[idx].push([key, value]);
                    } else {
                        newTable[idx] = [[key, value]];
                    }
                })
            }
        })
        this.table = newTable
    }

    setItem = (key, value) => {
        this.numItems++;
        const loadFactor = this.numItems/this.table.length;
        if (loadFactor > .8) {
            // resize
            this.resize();
        }
        const idx = hashStringToInt(key, this.table.length)
        if (this.table[idx]) {
            this.table[idx].push([key, value]);
        } else {
            this.table[idx] = [[key, value]];
        }
    }
    
    getItem = (key) => {
        const idx = hashStringToInt(key, this.table.length)
        if (!this.table[idx]) {
            return null;
        }

        return this.table[idx].find(x => x[0] === key)[1];
    }
}

const myTable = new HashTable();
myTable.setItem("firstName", "John");
myTable.setItem("lastName", "Irle");
myTable.setItem("age", 30);
myTable.setItem("dob", "08/15/2020");

console.log(myTable.getItem("firstName"))
console.log(myTable.getItem("lastName"))
console.log(myTable.getItem("age"))
console.log(myTable.getItem("dob"))