Question

我试图按顺序打印每个人的姓名，但我一直收到此错误family[i] is undefined。

function Person (name, age) {
    this.name = name;
    this.age = age;
}

var family = new Array();
family[0] = new Person("alice", 40);
family[1] = new Person("bob", 42);
family[2] = new Person("michelle", 8);
family[3] = new Person("timmy", 6);

for(var i = 0; i <= family.length; i++) {
    console.log(family[i].name);
}

Answer 1

您的for循环超出了数组的范围。尝试：

for( var i = 0; i < family.length; i++ )

请记住，array.length将始终高于最大数组索引，因为索引从0开始，而length从1开始。

Answer 2

在尝试读取末尾的未定义值时，按如下方式编辑for循环：

for(var i = 0; i <= family.length; i++) {
    console.log(family[i].name);
}

到

for(var i = 0; i < family.length; i++) {
    console.log(family[i].name);
}

试图访问数组：family [i]未定义

2 个答案: