js & void() & void(0) All In One

js & void() & void(0) All In One

https://www.runoob.com/js/js-void.html

void()

<a href="javascript:void(0)">单击此处什么也不会发生</a>
<a href="javascript:void(alert('Warning!!!'))">点我!</a>

function getValue(){
   var a,b,c;
   a = void( b = 5, c = 7 );
   document.write('a = ' + a + ' b = ' + b +' c = ' + c );
}

// a = undefined b = 5 c = 7

js void 0 & undefined All In One

TypeScript void

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://gist.github.com/xgqfrms/f7196dc9f76ba13a80163fb6f910ed3b

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