是否存在具有不同值的数据类型，例如 boolean

Question

Is there a datatype in javaScript or PHP etc. that can contain just a view different custom values. Like a boolean but with three types. Like something like this:
the value must be one of the following things "above", "under" or "in the middle".

Answer 1

Hey in JavaScript there is no such thing, but you can use number and create some kind of enum like this

const ENUM = {
  ABOVE: 1,
  MIDDLE: 0,
  UNDER: -1
}

and then use it like this:

function acceptValue(en) {
  if (en === ENUM.ABOVE) {
    /* do something */
  }
}

Answer 2

Not in PHP, but you could build your custom types like this:

class catLocation
{
    protected $val;
    protected $allowed = ['on', 'under'];

    public function __construct(string $val)
    {
        if(!in_array($val, $this->allowed)) {
            throw new InvalidArgumentException('catLocation must be on or under');
        }
        $this->val = $val;
    }

    public function __invoke()
    {
         return $this->val;   
    }
}

... typehint it in your function definitions:

function whereIsCat(catLocation $loc) {
    return 'The cat is ' . $loc() . ' the table.'; 
    // Calling your object like a function will call the "magic" __invoke() method
}

... and use it like that:

$kitty_loc = new catLocation('under');

echo whereIsCat($kitty_loc); // The cat is under the table.

Answer 3

solution from this website: https://www.sohamkamani.com/blog/2017/08/21/enums-in-javascript/

const seasons = {
  SUMMER: {
    BEGINNING: "summer.beginning",
    ENDING: "summer.ending"
  },
  WINTER: "winter",
  SPRING: "spring",
  AUTUMN: "autumn"
};

let season = seasons.SUMMER.BEGINNING;

if (!season) {
  throw new Error("Season is not defined");
}

switch (season) {
  case seasons.SUMMER.BEGINNING:
  // Do something for summer beginning
  case seasons.SUMMER.ENDING:
  // Do something for summer ending
  case seasons.SUMMER:
  // This will work if season = seasons.SUMMER
  // Do something for summer (generic)
  case seasons.WINTER:
  //Do something for winter
  case seasons.SPRING:
  //Do something for spring
  case seasons.AUTUMN:
  //Do something for autumn
}