我试图提醒"70"和"John"，但相反，我收到了警报"[object Object]"

Question

我试图提醒"70"和"John"，但相反，我收到警报"[对象对象]"。我不知道为什么。

<p>
<script>
var Car = function(maxSpeed, driver) {
this.maxSpeed = maxSpeed;
this.driver = driver;
}
var myCar = new Car(70, "John");
window.alert(myCar);
</script>
</p>

https://js.do/code/244719

Answer 1

window.alert(myCar.maxSpeed+"and"+ myCar.driver);

Answer 2

使用JSON.stringfy

var Car = function(maxSpeed, driver) {
this.maxSpeed = maxSpeed;
this.driver = driver;
}
var myCar = new Car(70, "John");
window.alert(JSON.stringify(myCar))

Answer 3

另一种方法是通过设置toString方法来设置对象作为字符串调用时应显示的内容。 除非您知道自己在做什么，否则不一定建议这样做，但该示例是合适的：

var Car = function(maxSpeed, driver) {
this.maxSpeed = maxSpeed;
this.driver = driver;
this.toString = () => [this.maxSpeed,this.driver].join(' and ')
}
var myCar = new Car(70, "John");
window.alert(myCar);