empty.js

// 8 March 2024
// check that given value contains no values or is an empty array, string, object...

// from simplegraph repo 2014
// https://github.com/dfkaye/simplegraph/

// simpler than the is-empty.js gist 5 Jan 2018
// https://gist.github.com/dfkaye/f87272098c4e19e4d55a6a18515aefce

// 24 May 2024
// added non-empty prototype case,
// added comparison test file for empty() and isEmpty()

function empty(o) {
  for (var k in Object(o)) {
    return false;
  }
  return true;
}

/* test it out */

console.log(
  empty(''), // true
  empty(' '), // false - has an index { 0 : ' ' }
  empty({}), // true
  empty({ a: '' }), // false

  '\narrays\n',
  empty([]), // true
  empty([ '' ]), // false - has an index { 0 : '' }
  empty(Array(1)), // true - because slot is [empty] (not undefined or even null)
  empty(Array(1).fill(1)), // false - slot has a value
  empty(Array(1).fill()), // false - slot has been assigned `undefined`

  '\nnumber and boolean\n',
  empty( 1 ), // true - has no own properties
  empty( 0 ),  // true - has no own properties
  empty(true), // true - has no own properties
  empty(false), // true - has no own properties

  '\nundefined and null\n',
  empty(), // true - not "empty" but has no value
  empty(null), // true - not "empty" but has no value

  '\nNaN\n',
  empty(NaN), // true

  // added 24 may 2024
  '\nObject.create\n',
  empty(Object.create({p: 42})) // should be false
);

test.js

// 24 May 2024
// console tests for empty and isEmpty to show that empty() reports false for an
// object with an enumerable prototype property whereas isEmpty() reports true for
// such an object if it has no "own" properties.

+(function () {
  console.group("empty");

  function empty(o) {
    for (var k in Object(o)) {
      return false;
    }
    return true;
  }

  /* test it out */

  console.log(
      empty(''), // true
      empty(' '), // false - has an index { 0 : ' ' }
      empty({}), // true
      empty({ a: '' }), // false

      '\narrays\n',
      empty([]), // true
      empty([ '' ]), // false - has an index { 0 : '' }
      empty(Array(1)), // true - because slot is [empty] (not undefined or even null)
      empty(Array(1).fill(1)), // false - slot has a value
      empty(Array(1).fill()), // false - slot has been assigned `undefined`

      '\nnumber and boolean\n',
      empty( 1 ), // true - has no own properties
      empty( 0 ),  // true - has no own properties
      empty(true), // true - has no own properties
      empty(false), // true - has no own properties

      '\nundefined and null\n',
      empty(), // true - not "empty" but has no value
      empty(null), // true - not "empty" but has no value

      '\nNaN\n',
      empty(NaN), // true

      '\nObject.create\n',
      empty(Object.create({p: 42})) // should be false
  );

  console.groupEnd("empty");
})()


+(function () {
  console.group("isEmpty");

  function isEmpty(value) {
    return Object.values(Object(value)).length == 0
  }

  /* test it out */

  console.log(
      isEmpty(''), // true
      isEmpty(' '), // false - has an index { 0 : ' ' }
      isEmpty({}), // true
      isEmpty({ a: '' }), // false

      '\narrays\n',
      isEmpty([]), // true
      isEmpty([ '' ]), // false - has an index { 0 : '' }
      isEmpty(Array(1)), // true - because slot is [empty] (not undefined or even null)
      isEmpty(Array(1).fill(1)), // false - slot has a value
      isEmpty(Array(1).fill()), // false - slot has been assigned `undefined`

      '\nnumber and boolean\n',
      isEmpty( 1 ), // true - has no own properties
      isEmpty( 0 ),  // true - has no own properties
      isEmpty(true), // true - has no own properties
      isEmpty(false), // true - has no own properties

      '\nundefined and null\n',  
      isEmpty(), // true - not "empty" but has no value
      isEmpty(null), // true - not "empty" but has no value

      '\nNaN\n',
      isEmpty(NaN), // ture

      '\nObject.create\n',
      isEmpty(Object.create({p: 42})) // true - but should it be...?
  );

  console.groupEnd("isEmpty");
})()