@etianen/dict

Helpers for treating dicts as maps.

Installing

npm install '@etianen/dict'

TypeScript: To take advantage of typings, be sure to set moduleResolution to "node" in your tsconfig.json.

Overview

Treating dicts as maps in Javascript is needlessly difficult.

@etianen/dict provides a minimal set of helpers of interacting with dicts.

import * as dict from "@etianen/dict";

dict.has({foo: "bar"}, "foo");  // => true
dict.mapValues({foo: "bar"}, v => v.toUpperCase());  // => {foo: "BAR"}

API

In all the functions below:

• Only own, enumerable properties are considered.
• The source arguments are never mutated.
• If the return value is a Dict or Array, it is frozen.

Dict

An object containing values of type V.

type Dict<V> = {[key: string]: V};

count()

Returns the number of entries in dict.

Note: This is an O(n) operation. Use isEmpty() if you just want to check if the dict is empty.

function count(dict: Dict<Object>): number;

empty()

Returns a new empty dict.

function empty<V>(): Dict<V>;

entries()

Returns an Array of [key, value] entries in dict.

function entries<V>(dict: Dict<V>): Array<[string, V]>;

every()

Returns true if all entries in dict satisfy predicate.

function every<V>(dict: Dict<V>, predicate: (value?: V, key?: string, dict?: Dict<V>) => boolean, context?: Object): boolean;

filter()

Returns a new dict containing entries from dict that satisfy predicate.

function filter<V>(dict: Dict<V>, predicate: predicate: (value?: V, key?: string, dict?: Dict<V>) => boolean, context?: Object): Dict<V>

forEach()

Runs sideEffect for each entry in dict.

function forEach<V>(dict: Dict<V>, sideEffect: (value?: V, key?: string, dict?: Dict<V>) => void, context?: Object): void;

fromEntries()

Creates a new dict from an array of [key, value] entries.

function fromEntries<V>(entries: Array<[string, V]>): Dict<V>;

fromKeys()

Creates a new dict from an array of keys, obtaining the values by passing each key through mapper.

function fromKeys<V>(keys: Array<string>, mapper: (key?: string, index?: number, array?: Array<string>) => V, context?: Object): Dict<V>

get()

Returns the value at key in dict, or defaultValue if the key is not set.

function get<V>(dict: Dict<V>, key: string, defaultValue?: V): V;

has()

Returns true if key is in dict.

function has(dict: Dict<Object>, key: string): boolean;

isEmpty()

Returns true if dict contains no entries.

function isEmpty(dict: Dict<Object>): boolean;

keys()

Returns an Array of all keys in dict.

function keys(dict: Dict<Object>): Array<string>;

map()

Returns a new Array with all entries passed through mapper.

function map<V, R>(dict: Dict<V>, mapper: (value?: V, key: string, dict?: Dict<V>) => R, context?: Object): Array<R>

mapEntries()

Returns a new dict with all entries passed through mapper.

function mapEntries<V, R>(dict: Dict<V>, mapper: (value?: V, key: string, dict?: Dict<V>) => [string, R], context?: Object): Dict<R>

mapKeys()

Returns a new dict with all keys passed through mapper.

function mapKeys<V>(dict: Dict<V>, mapper: (key?: string, value? V, dict?: Dict<V>) => string, context?: Object): Dict<V>;

mapValues()

Returns a new dict with all values passed through mapper.

map<V, R>(dict: Dict<V>, mapper: (value?: V, key?: string, dict?: Dict<V>) => R, context?: Object): Dict<R>;

reduce()

Reduces dict to a single value using reducer.

function reduce<V>(dict: Dict<V>, reducer: (reduction?: V, value?: V, key?: string, dict?: Dict<V>) => V): V;
function reduce<V, R>(dict: Dict<V>, reducer: (reduction?: R, value?: V, key?: string, dict?: Dict<V>) => R, initialReduction: R, context?: V;

remove()

Returns a new dict with key removed.

function remove<V>(dict: Dict<V>, key: string): Dict<V>;

set()

Returns a new dict with key set to value.

function set<V>(dict: Dict<V>, key: string, value: V): Dict<V>;

some()

Returns true if one or more entries in dict satisfy predicate.

function some<V>(dict: Dict<V>, predicate: (value?: V, key?: string, dict?: Dict<V>) => boolean, context?: Object): boolean;

update()

Returns a copy of dict updated with all entries in other.

function update<V>(dict: Dict<V>, other: Dict<V>): Dict<V>;

values()

Returns an Array of all values in dict.

function values<V>(dict: Dict<V>): Array<V>;

Build status

This project is built on every push using the Travis-CI service.

Support and announcements

Downloads and bug tracking can be found at the main project website.

More information

This project was developed by Dave Hall. You can get the code from the project site.

Dave Hall is a freelance web developer, based in Cambridge, UK. You can usually find him on the Internet:

• Website
• Google Profile