rust-map v2.0.2

Rust Map

A class that extends the basic JS Map with some of the Rust HashMap api's.

Example

The entry method returns an object representing an entry into the map.

orInsert

If the entry does not exist, then the value passed to orInsert is returned. It is also inserted into the map for future accesss.

import { RustMap } from "rust-map";

const m = new RustMap();
const v = m.entry("key").orInsert(10);

console.assert(v === 10);
console.assert(m.get("key") === 10);

If the entry already exists, then the existing value will be returned.

import { RustMap } from "rust-map";

const m = new RustMap();

m.set("key", 40);

const v = m.entry("key").orInsert(10);

console.assert(v === 40);

orInsertWith

orInsertWith is the same as orInsert except that it takes a function that returns the value to insert. It won't call the function if the entry already existed. This is ideal for situations where calculate for the default value is complex.

import { RustMap } from "rust-map";

function reallyComplicatedCalculation() {
    // Lots of code...
    return "value";
}

const m = new RustMap();

// Bad!
// const v = m.entry("key").orInsert(reallyComplicatedCalculation());

// Good!
const v = m.entry("key").orInsertWith(reallyComplicatedCalculation);

orInsertWith can also accept function arguments if your calculation requires arguments

import { RustMap } from "rust-map";

function calculationWithArguments(numberOfGeeseInTheWorld, nameOfTheKing) {
    // lots of code...
    return "value";
}

const m = new RustMap();
const v = m.entry("key").orInsertWith(reallyComplicatedCalculation, 100, "Jim Bob");

orConstruct

If your map values are classes, you can use orConstruct instead of orInsertWith. It will call new on the type passed. It also accepts arguments incase your class requires constructor arguments.

import { RustMap } from "rust-map";

class MyMapValue {
    constructor(theFirstArgument) {
        // constructor code...
    }
}

const m = new RustMap();
const v = m.entry("key").orConstruct(MyMapValue, "This is the first argument");

retain

import { RustMap } from "rust-map";

const m = new RustMap([
    ["one", 1],
    ["two", 2],
    ["three", 3],
    ["four", 4],
    ["five", 5],
    ["six", 6],
    ["seven", 7],
]);

console.assert(m.size === 7);

// Remove all the entries that have odd values.
m.retain((_key, value) => value % 2 === 0);

console.assert(m.size === 3);