JS how to return the dogs that match a select breed?

Question

I am new to coding and cannot workout why my code is not working. Dose anyone have any suggestion of how to fix it?

The question I have been given is this;

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']

This is the code I have written;

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
}

My code will be run against this;

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"]);
    });
});

This is the error that I am being given;

Answer 1

您刚刚创建了一些名称数组，您需要哈巴狗的名称，您可以使用过滤器像 pugs.filter(p => p.breed === 'pug') 这样的数组，这将为您提供一个仅包含 pug 元素的数组（检查过滤文档），而不仅仅是使用 map 从中取名，map 根据给定的回调函数转换您的数组，该函数接受数组元素并且必须返回新元素（检查 array.map）

Answer 2

pugs.push[i].name is a mistake. You should have pugs.push(dogs[i].name); .

Also, you don't really need a regex for pug . Just check like this:

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

Answer 3

You regular expression is /(pug)/g where it should be /(Pug)/g . But in my opinion if don't even need to use Regex. When it's direct comparison between strings you can use the comparison operator == or === . Other issue in your code it's how you are pushing to the array. Should be pugs.push(dogs[i].name) and not pugs.push[i].name . Therefore this is my suggestion:

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

I corrected your version and created an easier version for you. Here it goes:

 //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));

You had some errors.

• First you have a typo on breed. You wrote 'bread' instead.
• you have to set reg.lastIndex = 0 because regex, called several times may return different results
• you had a syntax error on push,
• regex must be case insensitive

Hope it helps you.

Answer 5

Within the code you wrote:

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
}

You had some typos and errors. First off, you don't really need a regular expression to check the dog breed - see my if statement:

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

(You also had a typo - you spelled breed with an a, like bread .)

Secondly, your syntax for Array.prototype.push() is wrong - it should be this:

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

So after you've done all that, your code should look like this:

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;
}

---

However, if you really wanted to make the code smaller and faster, you could use Array.prototype.filter() and ES6 arrow functions like so:

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