函数加new与不加new区别

没有设置返回值 function fruit(type) { this.type = type; console.log("this====", this); } let fruit1 = new fruit("apple"); // fruit {type: "apple"} let fruit2 = fruit("apple"); //window console.log('fruit1', fruit1) //fruit {type: "apple"} console.log('fruit2', fruit2) //undefined 设置返回值 类型为String Boolean Number function fruit(type) { this.type = type; console.log("this====", this); return this.type; } let fruit1 = new fruit("banana"); // fruit {type: "banana"} let fruit2 = fruit("banana"); //window console.log('fruit1', fruit1) //fruit {type: "banana"} console.log('fruit2', fruit2) //"banana" 设置返回值 类型为Object Array Function function fruit(type) { this.type = type; console.log("this====", this); return { type: this.type }; } let fruit1 = new fruit("pear"); // fruit {type: "pear"} let fruit2 = fruit("pear"); //window console.log('fruit1', fruit1) //{type: "pear"} console.log('fruit2', fruit2) //{type: "pear"}

总结: 一个是函数调用 一个是对象实例创建