isPrimitive() - Determines if `input` is a primitive value or not.

isPrimitive.js

/**
 * Determines if `input` is a primitive value or not.
 * @param {any} input
 *   The input value to test.
 * @returns {boolean}
 *   Returns `true if `input` is a primitive, otherwise `false` is returned.
 */
function isPrimitive(input) {
  if (input == null) {
    // This is here to correctly handle document.all.
    return input === null || input === undefined;
  }
  const type = typeof input;
  return type !== "object" && type !== "function";
}