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Kind

A more precise version of JavaScript's typeof

npm package Build Status Downloads Issues Code Coverage Semantic Release

Description

kind() returns a useful name for a variable's type. It breaks down objects into more precise terms: array, null, element, etc.

Examples:

Input typeof kind
[1, 2, 3] "object" "array"
null "object" "null"
document.getElementById('id') "object" "element"
document.getElementsByTagName('div') "object" "nodelist"
document.createTextNode('') "object" "node"
new Date() "object" "date"
{} "object" "object" (if no special type was detected — see full list below)

Install

yarn: yarn add kindjs

npm: npm install kindjs

Usage

import kind from 'kindjs';

kind(['hello', 'world']);
//=> 'array'

Basic

// Objects that aren't *really* objects
kind(null);       // "null"
kind([1, 2, 3]);  // "array"
kind(arguments);  // "arraylike"
kind(new Date()); // "date"
kind(document.getElementById('id'));        // "element"
kind(document.getElementsByTagName('div')); // "nodelist"

// This one's actually just an object
kind({});         // "object"

// Also works on standard types
kind("text");     // "string"
kind(2);          // "number"
kind(alert);      // "function"

"Deep" option

You may add a second, boolean parameter to tell kind to perform a deeper test for some types. For example, instead of "number" it could return "integer" or "float".

kind(1);          // "number"
kind(1, true);    // "integer"

kind(1.21);       // "number"
kind(1.21, true); // "float"

kind(evt);        // "event"
kind(evt, true);  // "mouseevent" (i.e. if the event was a click)

A complete list is noted below

Supported types

  • All standard types normally returned by typeof:
    • function, undefined, boolean
    • string
      • Deep option returns either string or emptystring
    • number
      • Deep option returns either integer or float
  • array
  • arraylike
    • A non-array object with a .length property
  • null
  • element
  • node
    • Deep options from this list (e.g. text, comment)
  • nodelist
  • event
    • Deep options from this list (e.g. mouseevent, keyboardevent)
  • regexp
  • date
  • error
  • errorevent
  • math

Features

  • Works with any type, not just objects
  • Always returns a simple lowercase string, just like the native typeof
  • Handles undefined or undeclared variables
  • Optimized to check for the most common types first
  • Excellent browser support, including many very old browsers
    • IE 6+ (and maybe older)
    • Chrome
    • Firefox
    • Safari
    • Android 1+
    • Opera (pre-Blink)
    • Netscape 4 (in theory!)
    • Probably anything that runs JavaScript and supports regular expressions