Vote for Espruino features!

Here is a semi complete map poly of a older project of mine.

'use strict';

class Map
{
    constructor (keyVal)
    {
        this.clear();

        if (Array.isArray(keyVal)) {
            keyVal.forEach(kv => this._keys.push(kv[0]) && this._values.push(kv[1]));
        }
    }

    get size ()
    {
        return this._keys.length;
    }

    has (key)
    {
        return this._keys.includes(key);
    }

    get (key)
    {
        return this._values[this._keys.indexOf(key)];
    }

    set (key, value)
    {
        let i = this._keys.indexOf(key);

        if (i !== -1) {
            this._values[i] = value;
        } else {
            this._keys.push(key);
            this._values.push(value);
        }
    }

    delete (key)
    {
        let i = this._keys.indexOf(key);

        if (i === -1) {
            return false;
        }

        this._keys.splice(i, 1);
        this._values.splice(i, 1);
    }

    keys ()
    {
        return this._keys;
    }

    values ()
    {
        return this._values;
    }

    clear ()
    {
        this._keys = [];
        this._values = [];
    }

    entries ()
    {
        return this._iterator();
    }

    _iterator ()
    {
        let i = 0;

        return {
            next: () => i < this._keys.length ? {value: [this._keys[i], this._values[i++]], done: false} : {done: true}
        };
    }

    forEach (callback, scope = null)
    {
        this._keys.forEach(key => callback.call(scope, this.get(key), key, this));
    }
}

Amazingly close to what @Gordon already had :D