testem/lib/utils/isa.js

Test'em 'scripts! Javascript Unit testing made easy.

/*

isa.js
======

This is an `isa()` function that does simple and elegant type checking.
Examples:

  isa([], Array) // true
  isa(function(){}, Function) // true
  isa("abc", String) // true

*/
'use strict';

const toString = Object.prototype.toString;

function typeName(ctr) {
  return ctr.name || String(ctr).match(/function (.{1,})\(/)[1];
}

function objTypeName(obj) {
  return toString.call(obj).match(/^\[object (.*)\]$/)[1];
}

module.exports = function isa(obj, type) {
  if (obj === null || obj === undefined) {
    return false;
  }

  return obj instanceof type || // the straight-forward case
    obj.constructor === type || // .constructor check to catch the primitives case
    objTypeName(obj) === typeName(type); // name-based check for the cross window case
};