HackerRank Join Question

join.js

var left = [
    "apple",
"grape",
"grape",
"melon"
]

var right = [
    "grape",
"lemon",
"apple"
]

match('left', left, right)

/*
 * Complete the function below.
 */
function match(matchtype, left, right) {
    //console.log(matchtype, left, right)
    if (matchtype == 'left') {
        return leftjoin(left, right)
    } else if (matchtype == 'right') {
        return rightjoin(left, right)
    } else if (matchtype == 'inner') {
        return innerjoin(left, right)
    }
}

function leftjoin(A, B) {
    //idx of left + match in right or no match
    var h = hash(B)
    var rows = []
    for(var i = 0; i < A.length; i++) {
        var r = h[A[i]]
        if (r === undefined) {
            r = []
        }
        for (var j = 0; j < r.length; j++) {
            rows.push([i, r[j]])
            console.log(i, r[j])
        }
        if (r.length == 0) {
            rows.push([i, -1])
            console.log(i, -1)
        }
    }
    return rows
}

function rightjoin(A, B) {
    //idx of left + match in right or no match
    var h = hash(A)
    var rows = []
    for(var i = 0; i < B.length; i++) {
        var r = h[B[i]]
        if (r === undefined) {
            r = []
        }
        for (var j = 0; j < r.length; j++) {
            rows.push([r[j], i])
            console.log(r[j], i)
        }
        if (r.length == 0) {
            rows.push([-1, i])
            console.log(-1, i)
        }
    }
    return rows
}

function innerjoin(A, B) {
    var h = hash(B)
    var rows = []
    for(var i = 0; i < A.length; i++) {
        var r = h[A[i]]
        if (r) {
            for (var j = 0; j < r.length; j++) {
                rows.push([i,r[j]])
                console.log(i, r[j])
            }
        }
    }
    return rows   
}

function hash(A) {
    var h = {}
    for (var i = 0; i < A.length; i++) {
        if (!h[A[i]]) {
            h[A[i]] = []
        }
        h[A[i]].push(i)
    }
    return h
}