Question

我正在尝试在Codewars上解决以下Javascript kata，但出现“ undefined”。能否请别人向我展示“未定义”的确切含义。我正在努力了解下面的代码缺少的内容。干杯。

链接到挑战：https://www.codewars.com/kata/training-js-number-5-basic-data-types-object

我已经搜索了FreeCodeCamp JS OOP和Basic教程/课程，以发现类似的问题。通过StackOverflow，Reddit和Google搜索了许多网站以查找类似的挑战。下面的代码：

function animal(name, legs, color) {
  this.name = name;
  this.legs = legs;
  this.color = color;
}
var dog = new animal("dog", 4, "white");
// similar variables set such for other animal objects.
animal.prototype.toString = function animalToString() {
  var sent = "This " + this.color + " " + this.name + " has " + this.legs + " legs.";
  return sent;
}
return animal.prototype.toString.call();

预期：This white dog has 4 legs.，而不是：undefined

Answer 1

1）基于“说明”

给您一个函数动物，接受1个参数obj，例如：{name：“ dog”，legs：4，color：“ white”}，并返回如下字符串：“此白狗有4条腿。” < / p>

function animal({name, legs, color}) {
    return `The ${color} ${name} has ${legs} legs.`;
}

2）根据您应该学习的内容

function animal({name, legs, color}) {
  this.name = name;
  this.legs = legs;
  this.color = color;
}

animal.prototype.toString = function animalToString() {
  return `The ${this.color} ${this.name} has ${this.legs} legs.`;
}

var dog = new animal({name:"dog", legs:4, color:"white"});
dog.toString();

Answer 2

尝试一下：

function animal(obj){
  var newAnimal = {
    name: obj.name,
    legs: obj.legs,
    color: obj.color
  };


return "This " + newAnimal.color + " " + newAnimal.name + " has " + newAnimal.legs + " legs.";
}

我相信本kata的目的是向您介绍javascript对象。更改函数“动物”的输入时会引发此问题。如果查看右下角的样本测试，则输入到您要进行的函数中的输入应仅接受一个参数，该参数是具有属性名称，支路和颜色的对象。您将此输入更改为三个单独的参数，而不只是一个。

或者您可以完全跳过分配，而直接像这样直接访问输入：

function animal(obj){

return "This " + obj.color + " " + obj.name + " has " + obj.legs + " legs.";
}

Answer 3

你可以试试这个

function animal(obj){
  var a={name:"dog",legs:4,color:"white"}
  return "This" + " " + a.color + " " +a.name + " " + "has" + " " + a.legs + " " + "legs.";
}

尝试使用对象属性中的值填充字符串-获取“未定义”

3 个答案: