Get Object Type using Object.toString()

get-obj-type.js

function getType(obj) {
  const type = Object.prototype.toString.call(obj);
  // toString returns '[object <type>]'
  // I only want the <type> value, so skip '[object ' chars and ending ']' char
  return type.substring(7, type.length-1);
}

const tests = [
  'str: ' + getType('foobar'),
  'num: ' + getType(10),
  'obj: ' + getType({greeting: 'hello'}),
  'arr: ' + getType([0, 1, 2]),
  'date: ' + getType(new Date()),
  'el: ' + getType(document.createElement('p')),
  'empty:' + getType(null),
  'window: ' + getType(window),
  'document: ' + getType(window.document),
  'document first child: ' + getType(window.document.firstChild),
  'document last child: ' + getType(window.document.lastChild),
  'body: ' + getType(window.document.body)
];

const testsOutput = document.createElement('div');
testsOutput.style.whiteSpace = 'pre';
testsOutput.textContent = tests.join('\n');
document.body.appendChild(testsOutput);