8 个有用的 JS 技巧
2021-04-29 13:29
标签：类型 不能 对象属性 red 基本数据类型 基本 条件 创建 关注 使用 grid ，需要重新创建原始数据，并且每行的列长度可能不匹配， 为了确保不匹配行之间的长度相等，可以使用 ES6 提供了从数组中提取惟一值的两种非常简洁的方法。不幸的是，它们不能很好地处理非基本类型的数组。在本文中，主要关注基本数据类型。 对象合并是很常见的事情，我们可以使用新的ES6特性来更好，更简洁的处理合并的过程。 另一种数组 map 的实现的方式，不用 Array.from 还可以接受第二个参数，作用类似于数组的 不再需要根据一个条件创建两个不同的对象，可以使用展开运算符号来处理。 有时候一个对象包含很多属性，而我们只需要其中的几个，这里可以使用解构方式来提取我们需要的属性。如一个用户对象内容如下： 我们需要提取出两个部分，分别是用户及用户信息，这时可以这样做: 早期，如果属性名需要是动态的，我们首先必须声明一个对象，然后分配一个属性。这些日子已经过去了，有了ES6特性，我们可以做到这一点。 在用例中，如果正在构建一个基于模板的 8 个有用的 JS 技巧 标签：类型 不能 对象属性 red 基本数据类型 基本 条件 创建 关注 原文地址：https://www.cnblogs.com/Object-L/p/12200775.html1. 确保数组值
Array.fill方法。let array = Array(5).fill(‘‘);
console.log(array); // outputs (5) ["", "", "", "", ""]
2. 获取数组唯一值
1 const cars = [
2 ‘Mazda‘,
3 ‘Ford‘,
4 ‘Renault‘,
5 ‘Opel‘,
6 ‘Mazda‘
7 ]
8 const uniqueWithArrayFrom = Array.from(new Set(cars));
9 console.log(uniqueWithArrayFrom); // outputs ["Mazda", "Ford", "Renault", "Opel"]
10
11 const uniqueWithSpreadOperator = [...new Set(cars)];
12 console.log(uniqueWithSpreadOperator);// outputs ["Mazda", "Ford", "Renault", "Opel"]
3.使用展开运算符合并对象和对象数组
1 // merging objects
2 const product = { name: ‘Milk‘, packaging: ‘Plastic‘, price: ‘5$‘ }
3 const manufacturer = { name: ‘Company Name‘, address: ‘The Company Address‘ }
4
5 const productManufacturer = { ...product, ...manufacturer };
6 console.log(productManufacturer);
7 // outputs { name: "Company Name", packaging: "Plastic", price: "5$", address: "The Company Address" }
8
9 // merging an array of objects into one
10 const cities = [
11 { name: ‘Paris‘, visited: ‘no‘ },
12 { name: ‘Lyon‘, visited: ‘no‘ },
13 { name: ‘Marseille‘, visited: ‘yes‘ },
14 { name: ‘Rome‘, visited: ‘yes‘ },
15 { name: ‘Milan‘, visited: ‘no‘ },
16 { name: ‘Palermo‘, visited: ‘yes‘ },
17 { name: ‘Genoa‘, visited: ‘yes‘ },
18 { name: ‘Berlin‘, visited: ‘no‘ },
19 { name: ‘Hamburg‘, visited: ‘yes‘ },
20 { name: ‘New York‘, visited: ‘yes‘ }
21 ];
22
23 const result = cities.reduce((accumulator, item) => {
24 return {
25 ...accumulator,
26 [item.name]: item.visited
27 }
28 }, {});
29
30 console.log(result);
31 /* outputs
32 Berlin: "no"
33 Genoa: "yes"
34 Hamburg: "yes"
35 Lyon: "no"
36 Marseille: "yes"
37 Milan: "no"
38 New York: "yes"
39 Palermo: "yes"
40 Paris: "no"
41 Rome: "yes"
42 */
4. 数组 map 的方法 (不使用Array.Map)
Array.map。map方法，用来对每个元素进行处理，将处理后的值放入返回的数组。如下： 1 const cities = [
2 { name: ‘Paris‘, visited: ‘no‘ },
3 { name: ‘Lyon‘, visited: ‘no‘ },
4 { name: ‘Marseille‘, visited: ‘yes‘ },
5 { name: ‘Rome‘, visited: ‘yes‘ },
6 { name: ‘Milan‘, visited: ‘no‘ },
7 { name: ‘Palermo‘, visited: ‘yes‘ },
8 { name: ‘Genoa‘, visited: ‘yes‘ },
9 { name: ‘Berlin‘, visited: ‘no‘ },
10 { name: ‘Hamburg‘, visited: ‘yes‘ },
11 { name: ‘New York‘, visited: ‘yes‘ }
12 ];
13
14 const cityNames = Array.from(cities, ({ name}) => name);
15 console.log(cityNames);
16 // outputs ["Paris", "Lyon", "Marseille", "Rome", "Milan", "Palermo", "Genoa", "Berlin", "Hamburg", "New York"]
5. 有条件的对象属性
nst getUser = (emailIncluded) => {
return {
name: ‘John‘,
surname: ‘Doe‘,
...emailIncluded && { email : ‘john@doe.com‘ }
}
}
const user = getUser(true);
console.log(user); // outputs { name: "John", surname: "Doe", email: "john@doe.com" }
const userWithoutEmail = getUser(false);
console.log(userWithoutEmail); // outputs { name: "John", surname: "Doe" }
6. 解构原始数据
const rawUser = {
name: ‘John‘,
surname: ‘Doe‘,
email: ‘john@doe.com‘,
displayName: ‘SuperCoolJohn‘,
joined: ‘2016-05-05‘,
image: ‘path-to-the-image‘,
followers: 45
...
}
1 let user = {}, userDetails = {};
2 ({ name: user.name, surname: user.surname, ...userDetails } = rawUser);
3
4 console.log(user); // outputs { name: "John", surname: "Doe" }
5 console.log(userDetails); // outputs { email: "john@doe.com", displayName: "SuperCoolJohn", joined: "2016-05-05", image: "path-to-the-image", followers: 45 }
7. 动态属性名
1 const dynamic = ‘email‘;
2 let user = {
3 name: ‘John‘,
4 [dynamic]: ‘john@doe.com‘
5 }
6 console.log(user); // outputs { name: "John", email: "john@doe.com" }
8.字符串插值
helper组件，那么这一点就会非常突出，它使动态模板连接容易得多。 1 const user = {
2 name: ‘John‘,
3 surname: ‘Doe‘,
4 details: {
5 email: ‘john@doe.com‘,
6 displayName: ‘SuperCoolJohn‘,
7 joined: ‘2016-05-05‘,
8 image: ‘path-to-the-image‘,
9 followers: 45
10 }
11 }
12
13 const printUserInfo = (user) => {
14 const text = `The user is ${user.name} ${user.surname}. Email: ${user.details.email}. Display Name: ${user.details.displayName}. ${user.name} has ${user.details.followers} followers.`
15 console.log(text);
16 }
17
18 printUserInfo(user);
19 // outputs ‘The user is John Doe. Email: john@doe.com. Display Name: SuperCoolJohn. John has 45 followers.‘