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string representations of node.js built-in objects

moatorres
moatorres
pushedAt 8 months ago

moatorres/typetags

TypeTags

String Representations of Node.js Built-in Objects

This package contains a list of default string representations of built-in objects and types of Node.js — see the full list here.

Features

  • Simple API
  • Comprehensive documentation and test set
  • No dependencies
  • Includes TypeScript d.ts files

Install

NPM

npm install typetags

Yarn

yarn add typetags

Usage

In the examples below console.log and toString calls are not shown.

The TypeTags object contains a set of properties, methods and predicates, each representing an object type.

The library exports a single object TypeTags.

import { TypeTags } from 'typetags'

const o = { foo: 'bar' }

if (TypeTags.get(o) !== TypeTags.Object) {
  doSomething()
}

We can use it to check if an object's type tag matches the default tag of a data type.

TypeTags.get({})
// → [object Object]
TypeTags.has(new Map())
// → true
TypeTags.of([1, '2', [3]])
// → [ '[object Number]', '[object String]', '[object Array]' ]

Bundles

esm

import { TypeTags } from 'typetags'

cjs

const { TypeTags } = require('typetags')

umd

<script src="dist/umd/typetags.min.js"></script>

Using TypeTags to detect Object Class

Every object has a toString() method that is automatically called when the object is to be represented as a text value or when an object is referred to in a manner in which a string is expected.

By default, the toString() method is inherited by every object descended from Object. If this method is not overridden in a custom object, toString() returns "[object type]", where type is the object type. The following code illustrates this:

const o = new Object()
o.toString() // → [object Object]

Although using toString() in this way is unreliable, as objects can change the behavior of Object.prototype.toString() this library might be helpful when you need to compare objects' tags inside a procedure call or if you just need a quick reference.

const { TypeTags } = require('typetags')

function isArray(value) {
  return typeof value === 'object' && TypeTags.get(value) === TypeTags.Array
}

Tests

jest --coverage

Test Suites: 66 passed, 66 total
Tests:       2 skipped, 417 passed, 419 total
Snapshots:   0 total
Time:        5.342 s
Ran all test suites.
✨  Done in 6.72s.

TypeScript

Using TypeScript? We've got you covered. Check out our d.ts declaration files.

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