js void 0 & undefined All In One

js void 0 & undefined All In One.md

js void 0 & undefined All In One

interface Animal {
  speak(): void;
}

class Dog implements Animal {
  food: string = '';
  // override 字类覆盖父类方法
  constructor(food: string) {
    // super();
    this.food = food;
  }
  speak() {
    console.log("wang!");
  }
  eat(food: string) {
    // ?? => !== null && !== void 0 ? : 
    // void 0 === undefined
    console.log(food ?? this.food);
  }
}
const puppy = new Dog('meat');
puppy.speak();
puppy.eat('🐶');

"use strict";
class Dog {
    // override 字类覆盖父类方法
    constructor(food) {
        this.food = '';
        // super();
        this.food = food;
    }
    speak() {
        console.log("wang!");
    }
    eat(food) {
        // ?? => !== null && !== void 0 ? : 
        // void 0 === undefined
        console.log(food !== null && food !== void 0 ? food : this.food);
    }
}
const puppy = new Dog('meat');
puppy.speak();
puppy.eat('🐶');

void anything === undefined

void 0 === undefined;
// true

// void 0;
// undefined
void 1;
// undefined
// oid {};
// undefined
void [];
// undefined

void;
// Uncaught SyntaxError: Unexpected token ';'

https://www.typescriptlang.org/play?ssl=23&ssc=17&pln=1&pc=1#code/JYOwLgpgTgZghgYwgAgIImAWzgG2QbwFgAoZZAZwAcI4BrACgEoAuZANwHtgATAbhIC+JEghxxy5ZABEOAc2RZKOCJgjhJ6LLgIkyMDh26tyYKKHkBeZAHJr-UsgD0j5BzbQz3FIHVtQN4+gMMjANbdANidfQE7TQFWbXWQEDhATKABXBDAOKHp9Q2NTc0YdBzJnCkTqdMZ7MjIwAAtgcgA6TO5kKyaK5CEHKhoGPKICmLjyDmV6nDl6ACIAdzgQWQBCSfLozrIaMAyDIwoc+b7owpcAfmOWgD5kBYsrEEScPAAyR6ub9i5mgAZkM9ZDpxcnB4yG+NysiRAXhgoAg3H+sXiIwgYwmTR+ZxqdUa2xWDk6nQRJmQlBKlAAni1kCAINNpBNrKo4GBrLiSZRyfVunQmPY2RyNvRrIBeDcAbDss3hAA