Typescript / Javascript: using a tuple as a map key

Question

Hit this strange error in my code, and I cannot figure out how to get a constant time search from the map when using a tuple as my key.

Hope this illustrates the problem, and the workaround I'm using now to get it working:

hello.ts:

let map: Map<[number, number], number> = new Map<[number, number], number>()
    .set([0, 0], 48);

console.log(map.get([0,0])); // prints undefined

console.log(map.get(String([0, 0]))); //  compiler:  error TS2345: Argument of type 
// 'string' is not assignable to parameter of type '[number, number]'.

//the work-around:
map.forEach((value: number, key: [number, number]) => {
    if(String(key) === String([0, 0])){
        console.log(value); // prints 48
    }
})

To compile (move?) I use:

tsc hello.ts -target es6

tsc version 2.1.6

Tried a few things to get Map.get () to work, not having much success.

Answer 1

JavaScript ( , TypeScript), , , (.. ). , .

Maps , , , , :

const map: Map<[ number, number], number> = new Map<[ number, number ], number>();

const a: [ number, number ] = [ 0, 0 ];
const b: [ number, number ] = [ 0, 0 ];

// a and b have the same value, but refer to different arrays so are not equal
a === b; // = false

map.set(a, 123);
map.get(a); // = 123
map.get(b); // = undefined

, , :

const map: Map<string, number> = new Map<string, number>();

const a: [ number, number ] = [ 0, 0 ];
const b: [ number, number ] = [ 0, 0 ];

const astr: string = a.join(','); // = '0,0'
const bstr: string = b.join(','); // = '0,0'

// astr and bstr have the same value, and are strings so they are always equal
astr === bstr; // = true

map.set(astr, 123);
map.get(astr); // = 123
map.get(bstr); // = 123

Answer 2

, :

class MyMap {
    private map = new Map<string, number>();

    set(key: [number, number], value: number): this {
        this.map.set(JSON.stringify(key), value);
        return this;
    }

    get(key: [number, number]): number | undefined {
        return this.map.get(JSON.stringify(key));
    }

    clear() {
        this.map.clear();
    }

    delete(key: [number, number]): boolean {
        return this.map.delete(JSON.stringify(key));
    }

    has(key: [number, number]): boolean {
        return this.map.has(JSON.stringify(key));
    }

    get size() {
        return this.map.size;
    }

    forEach(callbackfn: (value: number, key: [number, number], map: Map<[number, number], number>) => void, thisArg?: any): void {
        this.map.forEach((value, key) => {
            callbackfn.call(thisArg, value, JSON.parse(key), this);
        });
    }
}

( )

, forEach, , [number, number] , .

:

let map = new MyMap();
map.set([1, 2], 4);
console.log(map.get([1, 2])) // 4

map.set([3, 4], 20);
map.forEach((v, k) => console.log(k, v));
// prints:
// [1, 2] 4
// [3, 4] 20