no-value: check whether value translates to null, undefined, NaN, or an empty string.

no-value.js

// 2 Aug 2019

// Check whether value translates to null, undefined, NaN, or an empty string.

// Comparable to the is-empty.js gist at https://gist.github.com/dfkaye/f87272098c4e19e4d55a6a18515aefce
// One major difference is that noValue asserts that [ '' ] has no value (true)
// whereas isEmpty asserts [ '' ] is *not* empty (false) due to { 0: ''}.

// Examples:
//  false is a value.
//  [] and [''] have noValue.
//  {"":""} and {} have noValue. -- added 6 April 2020
//  {"empty": ""} has noValue -- 17 April 2020
//  {"": "not empty"} has a value -- 17 April 2020

function noValue(o) {
  return !String(o == null || o !== o
      ? ''
    : Array.isArray(o)
      ? o
    : typeof o == 'object'
      ? Object.values(o)  // values, not keys
    : o).length;  
}

var tests = [
  // false
  0,
  [0],
  ['0'],
  {"": "not empty"},
  1,
  '2',
  true,
  false,
  ' ',

  // true
  null,
  undefined,
  NaN,
  '',
  [],
  [''],
  {},
  {"":""},
  {"empty": ""}
];

var results = tests.map(test => {
  var label = test === undefined ? 'undefined' : test !== test ? 'NaN' : test;
  return { test: label, result: noValue(test) };
});

console.log(JSON.stringify(results, null, 2));

/*
[
  {
    "test": 0,
    "result": false
  },
  {
    "test": [
      0
    ],
    "result": false
  },
  {
    "test": [
      "0"
    ],
    "result": false
  },
  {
    "test": {
      "": "not empty"
    },
    "result": false
  },
  {
    "test": 1,
    "result": false
  },
  {
    "test": "2",
    "result": false
  },
  {
    "test": true,
    "result": false
  },
  {
    "test": false,
    "result": false
  },
  {
    "test": " ",
    "result": false
  },
  {
    "test": null,
    "result": true
  },
  {
    "test": "undefined",
    "result": true
  },
  {
    "test": "NaN",
    "result": true
  },
  {
    "test": "",
    "result": true
  },
  {
    "test": [],
    "result": true
  },
  {
    "test": [
      ""
    ],
    "result": true
  },
  {
    "test": {},
    "result": true
  },
  {
    "test": {
      "": ""
    },
    "result": true
  },
  {
    "test": {
      "empty": ""
    },
    "result": true
  }
]
*/

test-go.js

// 30 July 2019
// wip

function go(arg) {
  var n = arg * 2;
  console.log(n === n);
  return n === n ? n : { arg, n };
}

/* test it out */

console.log(
  go(2),
  go('2'),
  go([1]),
  go([0.1]),
  go([]),
  go({})
);