Question

我是编码新手，无法锻炼为什么我的代码无法正常工作。剂量有人建议如何解决吗？

我得到的问题是这个；

This function takes an array of dog objects and returns an array of the names of all the pugs.
E.g. [
  {name: 'Beatrice', breed: 'Lurcher'},
  {name: 'Max', breed: 'Pug'},
  {name: 'Poppy', breed: 'Pug'}
]
will return ['Max', 'Poppy']

这是我编写的代码；

function getPugNames(dogs) {    
    let pugs = []
    let reg = /(pug)/g
    for (let i = 0; i < dogs.length; i ++) {
        if(reg.test(dogs[i].bread)) {
            pugs.push[i].name
        }
    } return pugs
}

我的代码将与此相对应；

describe("getPugNames", () => {
    it("returns [] when passed []", () => {
        expect(getPugNames([])).to.eql([]);
    });

    it("returns an array of pug names when passed an array of dog objects", () => {
        const dogs = [
            { name: "Beatrice", breed: "Lurcher" },
            { name: "Max", breed: "Pug" },
            { name: "Poppy", breed: "Pug" }
        ];
        expect(getPugNames(dogs)).to.eql(["Max", "Poppy"]);
        const dogs2 = [
            { name: "Steven", breed: "Lurcher" },
            { name: "Daphne", breed: "Pug" },
            { name: "Sandy", breed: "Labrador" },
            { name: "Mike", breed: "Pug" },
            { name: "Spike", breed: "Pug" }
        ];
        expect(getPugNames(dogs2)).to.eql(["Daphne", "Mike", "Spike"]);
        const dogs3 = [
            { name: "Kevin", breed: "Labrador" },
            { name: "Patch", breed: "Rottweiler" },
            { name: "Miles", breed: "Lurcher" },
            { name: "Sandy", breed: "Pug" },
            { name: "Spot", breed: "Pug" },
            { name: "Josephine", breed: "Terrier" },
            { name: "Eric", breed: "Pug" }
        ];
        expect(getPugNames(dogs3)).to.eql(["Sandy", "Spot", "Eric"]);
    });
});

这是我得到的错误；

Answer 1

您刚刚创建了一些名称数组，您需要使用pugs命名，您可以像pugs.filter（p => p.breed ==='pug'）这样使用数组过滤器，这只会为您提供一个带有pug的数组elements（检查过滤器文档），而不仅仅是使用map命名，map根据给定的回调函数转换数组，该回调函数接受数组元素并且必须返回新元素（check array.map）

Answer 2

pugs.push[i].name是一个错误。您应该有pugs.push(dogs[i].name);。

此外，您实际上并不需要pug的正则表达式。只需像这样检查：

if (dogs[i].breed.toLowerCase() === "pug")

Answer 3

您的正则表达式为/(pug)/g，应为/(Pug)/g。但是我认为，甚至不需要使用Regex。当直接在字符串之间进行比较时，可以使用比较运算符==或===。代码中的另一个问题是您如何推入数组。应该是pugs.push(dogs[i].name)，而不是pugs.push[i].name。因此，这是我的建议：

function getPugNames(dogs) {

  let pugs = []
  for (let i = 0; i < dogs.length; i ++) {
    if(dogs[i].bread === 'Pug') {
      pugs.push(dogs[i].bread)
    }
  } 

  return pugs
}

Answer 4

我更正了您的版本，并为您创建了更简单的版本。在这里：

//corrected version
function getPugNames(dogs) {    
    var pugs = [];
    var reg = /pug/gi
    for (let i = 0; i < dogs.length; i ++) {
        reg.lastIndex = 0;
        if (reg.test(dogs[i].breed)) 
            pugs.push(dogs[i].name);
    };
    return pugs
}

//easier version:
var getPugNames2 = dogs=>dogs
    .map(d=>d.breed.toLowerCase() == "pug" ? d.name : null)                    
    .filter(e=>e);

const dogs1 = [
    { name: "Beatrice", breed: "Lurcher" },
    { name: "Max", breed: "Pug" },
    { name: "Poppy", breed: "Pug" }
];
const dogs2 = [
    { name: "Steven", breed: "Lurcher" },
    { name: "Daphne", breed: "Pug" },
    { name: "Sandy", breed: "Labrador" },
    { name: "Mike", breed: "Pug" },
    { name: "Spike", breed: "Pug" }
];
const dogs3 = [
    { name: "Kevin", breed: "Labrador" },
    { name: "Patch", breed: "Rottweiler" },
    { name: "Miles", breed: "Lurcher" },
    { name: "Sandy", breed: "Pug" },
    { name: "Spot", breed: "Pug" },
    { name: "Josephine", breed: "Terrier" },
    { name: "Eric", breed: "Pug" }
];

console.log(getPugNames([]));
console.log(getPugNames(dogs1));
console.log(getPugNames(dogs2));
console.log(getPugNames(dogs3));
console.log(getPugNames2([]));
console.log(getPugNames2(dogs1));
console.log(getPugNames2(dogs2));
console.log(getPugNames2(dogs3));

您遇到了一些错误。

首先，您有一个错别字。您写的是“面包”。
您必须设置reg.lastIndex = 0，因为多次调用的正则表达式可能会返回不同的结果
您在推送时遇到语法错误，
regex必须不区分大小写

希望它对您有帮助。

Answer 5

在您编写的代码中：

function getPugNames(dogs) {    
    let pugs = []
    let reg = /(pug)/g
    for (let i = 0; i < dogs.length; i ++) {
        if(reg.test(dogs[i].bread)) {
            pugs.push[i].name
        }
    } return pugs
}

您有一些错别字和错误。首先，您真的不需要正则表达式来检查狗的品种-请参阅我的if声明：

if (dogs[i].breed == "Pug") {...}

（您也有错字-您用{拼写了breed，例如bread。）

第二，您对Array.prototype.push()的语法是错误的-应该是这样的：

pugs.push(dogs[i].name);

因此，在完成所有这些操作之后，您的代码应如下所示：

function getPugNames(dogs) {
    let pugs = [];
    for (let i = 0; i < dogs.length; i++) {
        if (dogs[i].breed == "Pug") {
            pugs.push(dogs[i].name);
        }
    }
    return pugs;
}

但是，如果您真的想使代码更小，更快，则可以像这样使用Array.prototype.filter()和ES6 arrow functions：

const getPugNames = (dogs) => dogs.filter(d => if (d.breed == "Pug") return d.name);

JS如何退回与精选犬匹配的狗？

5 个答案: