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);