freeCodeCamp/understand-own-properties.md at 41b7a331008a97d20155c3752b3beb530375ab99

Oliver Eyton-Williams 41b7a33100

fix: replace .chinese.md extension with .md

2020-09-29 22:09:05 +02:00

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id, title, challengeType, forumTopicId, localeTitle

id	title	challengeType	forumTopicId	localeTitle
587d7dae367417b2b2512b7b	Understand Own Properties	1	301326	了解自己的属性

Description

请看下面的实例，Bird构造函数定义了两个属性：name和numLegs：

function Bird(name) {
  this.name  = name;
  this.numLegs = 2;
}

let duck = new Bird("Donald");
let canary = new Bird("Tweety");

name和numLegs被叫做自身属性，因为他们是直接在实例对象上定义的。这就意味着duck和canary这两个对象分别拥有这些属性的独立副本。事实上，Bird的这些实例都将拥有这些属性的独立副本。以下的代码将duck里面所有的自身属性都存到一个叫ownProps的数组里面：

let ownProps = [];

for (let property in duck) {
  if(duck.hasOwnProperty(property)) {
    ownProps.push(property);
  }
}

console.log(ownProps); // prints [ "name", "numLegs" ]

Instructions

将canary对象里面的自身属性添加到ownProps数组里面。

Tests

tests:
  - text: "<code>ownProps</code>应该包含<code>'numLegs'</code>和<code>'name'</code>两个属性的值。"
    testString: assert(ownProps.indexOf('name') !== -1 && ownProps.indexOf('numLegs') !== -1);
  - text: 在不使用内置方法<code>Object.keys()</code>的情况下完成这个挑战。
    testString: assert(!/Object(\.keys|\[(['"`])keys\2\])/.test(code));
  - text: You should solve this challenge without hardcoding the <code>ownProps</code> array.
    testString: assert(!/\[\s*(?:'|")(?:name|numLegs)|(?:push|concat)\(\s*(?:'|")(?:name|numLegs)/.test(code));

Challenge Seed

function Bird(name) {
  this.name = name;
  this.numLegs = 2;
}

let canary = new Bird("Tweety");
let ownProps = [];
// Add your code below this line

Solution

function Bird(name) {
  this.name = name;
  this.numLegs = 2;
}

let canary = new Bird("Tweety");
function getOwnProps (obj) {
  const props = [];

  for (let prop in obj) {
    if (obj.hasOwnProperty(prop)) {
      props.push(prop);
    }
  }

  return props;
}

const ownProps = getOwnProps(canary);

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