identitate

A tiny custom identity function creator for composable softwares.

Table of contents

• Usage
• Pre-build methods
  • identity
  • identitySecond
  • identityLast
  • identitySecondLast
• Custom methods
  • createIdentity
• Browser support
• Development

Usage

import {createIdentity, identity, identitySecond, identityLast, identitySecondLast} from 'identitate';

// use built-in methods
console.log(identity('first', 'second', 'third', 'fourth', 'fifth')); // 'first'
console.log(identitySecond('first', 'second', 'third', 'fourth', 'fifth')); // 'second'
console.log(identityLast('first', 'second', 'third', 'fourth', 'fifth')); // 'fifth'
console.log(identitySecondLast('first', 'second', 'third', 'fourth', 'fifth')); // 'fourth'

// or create your own
const identityThird = createIdentity(2);
const identityThirdLast = createIdentity(-3);
const identityFirstNested = createIdentity(0, 'deeply[0].nested');

console.log(identityThird('first', 'second', 'third', 'fourth', 'fifth')); // 'third'
console.log(identityThirdLast('first', 'second', 'third', 'fourth', 'fifth')); // 'third'
console.log(identityFirstNested({deeply: [{nested: 'value'}]}, 'second', 'third', 'fourth', 'fifth')); // 'value'

Pre-built methods

identity

returns first argument passed to it

The classic identity function:

console.log(identity('first', 'second', 'third', 'fourth', 'fifth')); // 'first'

identitySecond

returns second argument passed to it

console.log(identitySecond('first', 'second', 'third', 'fourth', 'fifth')); // 'second'

Example usage when creating meta properties with the popular redux-actions package:

import {identity, identitySecond} from 'identitate';
import {createAction} from 'redux-actions';

export const doThing = createAction('DO_THING', identity, identitySecond);

console.log(doThing('payload', 'meta')); // {meta: 'meta', payload: 'payload', type: 'DO_THING'}

identityLast

returns last argument passed to it, regardless of total number of arguments

console.log(identityLast('first', 'second', 'third', 'fourth', 'fifth')); // 'fifth'
console.log(identityLast('first', 'second', 'third')); // 'third'

identitySecondLast

returns second-to-last argument passed to it, regardless of total number of arguments

console.log(identityLast('first', 'second', 'third', 'fourth', 'fifth')); // 'fourth'
console.log(identityLast('first', 'second', 'third')); // 'second'

Custom methods

createIdentity

creates a new identity method based on the parameters passed

createIdentity(position: number[, path: (Array<number|string>|number|string)]): any

// use a positive number to get the index of the arguments (zero-indexed)
const identityFourth = createIdentity(3);

console.log(identityLast('first', 'second', 'third', 'fourth', 'fifth')); // 'fourth'

// use a negative number to get the index of the arguments relative to the last
const identityThirdLast = createidentity(-3);

console.log(identityLast('first', 'second', 'third', 'fourth', 'fifth')); // 'third'

// include a path to get the deeply-nested value of that argument
const identityNested = createIdentity(0, 'deeply.nested');

console.log(identityNested({deeply: {nested: 'value'}})); // 'value'

The path parameter uses pathington under the hood for path parsing, so check there for valid values.

Browser support

• Chrome (all versions)
• Firefox (all versions)
• Edge (all versions)
• Opera 15+
• IE 9+
• Safari 6+
• iOS 8+
• Android 4+

Development

Standard stuff, clone the repo and npm install dependencies. The npm scripts available:

• build => run webpack to build development dist file with NODE_ENV=development
• build:minified => run webpack to build production dist file with NODE_ENV=production
• dev => run webpack dev server to run example app / playground
• dist => runs build and build-minified
• lint => run ESLint against all files in the src folder
• prepublish => runs compile-for-publish
• prepublish:compile => run lint, test:coverage, transpile:es, transpile:lib, dist
• test => run AVA test functions with NODE_ENV=test
• test:coverage => run test but with nyc for coverage checker
• test:watch => run test, but with persistent watcher
• transpile:lib => run babel against all files in src to create files in lib
• transpile:es => run babel against all files in src to create files in es, preserving ES2015 modules (for pkg.module)