isValue() checks that a value is not undefined, not null, not NaN, and not an empty string.

is-value.js

// 4 June 2020
// Value check that cuts through tiresome debates.

// Counterpart to isEmpty() which checks for empty containers.
// @see https://gist.github.com/dfkaye/f87272098c4e19e4d55a6a18515aefce

// Stricter version of noValue() from July 2019 which treats empty arrays and empty objects as
// not-containing-values.
// @see https://gist.github.com/dfkaye/e24b35e5cdc66b010cf95766f37ed4ca

/**
 * @function isValue() checks that an argument is a value. A value is not undefined, not null, not
 * NaN, and not an empty string (and not an empty String instance).
 *
 * @param {*}
 * @returns {boolean}
 */
function isValue(o) {
  var undef = o == null;
  var nan = o !== o;
  var empty = Object(o).valueOf() === '';

  return !(undef || nan || empty);
}

/* Test it out */

var shouldReturnFalse = [
  null,
  void 0,
  NaN,
  '',
  new String()
];

console.assert(shouldReturnFalse.every(item => !isValue(item)));

var shouldReturnTrue = [
  ' ',
  -0,
  false,
  [/* empty array */],
  {/* empty object */}
];

console.assert(shouldReturnTrue.every(item => isValue(item)));