README.md

HashMap.js

Java style HashMap for JavaScript. The key object must implement equals() and hashCode().

HashMap.js

function newBuckets (size) {
    let buckets = []
    for (let i = 0; i < size; i++) {
        buckets.push(null)
    }
    return buckets
}

function getBucket (key, buckets) {
    return key.hashCode() % buckets.length
}

class HashMap {
    constructor () {
        this.buckets = newBuckets(11)
        this.count = 0
    }
    get (key) {
        let bucket = getBucket(key, this.buckets)
        let entry = this.buckets[bucket]
        while (entry !== null) {
            if (entry.key.equals(key)) {
                return entry.value
            }
            entry = entry.next
        }
        return null
    }
    set (key, value) {
        let bucket = getBucket(key, this.buckets)
        let entry = this.buckets[bucket]
        while (entry !== null) {
            if (entry.key.equals(key)) {
                let prev = entry.value
                entry.value = value
                return prev
            }
            entry = entry.next
        }
        this.buckets[bucket] = {
            key: key,
            value: value,
            next: this.buckets[bucket]
        }
        if (++this.count === this.buckets.length) {
            let nextBuckets = newBuckets(this.buckets.length * 3)
            for (let entry of this) {
                let nextBucket = getBucket(entry.key, nextBuckets)
                nextBuckets[nextBucket] = {
                    key: entry.key,
                    value: entry.value,
                    next: nextBuckets[nextBucket]
                }
            }
            this.buckets = nextBuckets
        }
        return null
    }
    delete (key) {
        let bucket = getBucket(key, this.buckets)
        let entry = this.buckets[bucket]
        let prev = null
        while (entry !== null) {
            if (entry.key.equals(key)) {
                if (prev === null) {
                    this.buckets[bucket] = entry.next
                } else {
                    prev.next = entry.next
                }
                return key
            }
            prev = entry
            entry = entry.next
        }
        return null
    }
    *[Symbol.iterator] () {
        for (let i = 0; i < this.buckets.length; i++) {
            let entry = this.buckets[i]
            while (entry !== null) {
                yield entry
                entry = entry.next
            }
        }
    }
    *keys () {
        for (let entry of this) {
            yield entry.key
        }
    }
    *values () {
        for (let entry of this) {
            yield entry.value
        }
    }
}