几个牛X的js开发技巧

1. 确保数组值

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Array.fill方法。

let array = Array(5).fill(\'\');
console.log(array); // outputs (5) ["", "", "", "", ""]

2. 获取数组唯一值

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。

const cars = [
    \'Mazda\', 
    \'Ford\', 
    \'Renault\', 
    \'Opel\', 
    \'Mazda\'
]
const uniqueWithArrayFrom = Array.from(new Set(cars));
console.log(uniqueWithArrayFrom); // outputs ["Mazda", "Ford", "Renault", "Opel"]

const uniqueWithSpreadOperator = [...new Set(cars)];
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

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。

// merging objects
const product = { name: \'Milk\', packaging: \'Plastic\', price: \'5$\' }
const manufacturer = { name: \'Company Name\', address: \'The Company Address\' }

const productManufacturer = { ...product, ...manufacturer };
console.log(productManufacturer); 
// outputs { name: "Company Name", packaging: "Plastic", price: "5$", address: "The Company Address" }

// merging an array of objects into one
const cities = [
    { name: \'Paris\', visited: \'no\' },
    { name: \'Lyon\', visited: \'no\' },
    { name: \'Marseille\', visited: \'yes\' },
    { name: \'Rome\', visited: \'yes\' },
    { name: \'Milan\', visited: \'no\' },
    { name: \'Palermo\', visited: \'yes\' },
    { name: \'Genoa\', visited: \'yes\' },
    { name: \'Berlin\', visited: \'no\' },
    { name: \'Hamburg\', visited: \'yes\' },
    { name: \'New York\', visited: \'yes\' }
];

const result = cities.reduce((accumulator, item) => {
  return {
    ...accumulator,
    [item.name]: item.visited
  }
}, {});

console.log(result);
/* outputs
Berlin: "no"
Genoa: "yes"
Hamburg: "yes"
Lyon: "no"
Marseille: "yes"
Milan: "no"
New York: "yes"
Palermo: "yes"
Paris: "no"
Rome: "yes"
*/

4. 数组 map 的方法 (不使用Array.Map)

另一种数组 map 的实现的方式，不用 Array.map。Array.from 还可以接受第二个参数，作用类似于数组的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：

const cities = [
    { name: \'Paris\', visited: \'no\' },
    { name: \'Lyon\', visited: \'no\' },
    { name: \'Marseille\', visited: \'yes\' },
    { name: \'Rome\', visited: \'yes\' },
    { name: \'Milan\', visited: \'no\' },
    { name: \'Palermo\', visited: \'yes\' },
    { name: \'Genoa\', visited: \'yes\' },
    { name: \'Berlin\', visited: \'no\' },
    { name: \'Hamburg\', visited: \'yes\' },
    { name: \'New York\', visited: \'yes\' }
];
const cityNames = Array.from(cities, ({ name}) => name);
console.log(cityNames);
// outputs ["Paris", "Lyon", "Marseille", "Rome", "Milan", "Palermo", "Genoa", "Berlin", "Hamburg", "New York"]

5. 有条件的对象属性

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。

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

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：

const rawUser = {
   name: \'John\',
   surname: \'Doe\',
   email: \'john@doe.com\',
   displayName: \'SuperCoolJohn\',
   joined: \'2016-05-05\',
   image: \'path-to-the-image\',
   followers: 45
   ...
}

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:

let user = {}, userDetails = {};
({ name: user.name, surname: user.surname, ...userDetails } = rawUser);

console.log(user); // outputs { name: "John", surname: "Doe" }
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

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。

const dynamic = \'email\';
let user = {
    name: \'John\',
    [dynamic]: \'john@doe.com\'
}
console.log(user); // outputs { name: "John", email: "john@doe.com" }

8.字符串插值

在用例中，如果正

const user = {
  name: \'John\',
  surname: \'Doe\',
  details: {
    email: \'john@doe.com\',
    displayName: \'SuperCoolJohn\',
    joined: \'2016-05-05\',
    image: \'path-to-the-image\',
    followers: 45
  }
}
const printUserInfo = (user) => { 
  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.`
  console.log(text);
}

printUserInfo(user);
// outputs \'The user is John Doe. Email: john@doe.com. Display Name: SuperCoolJohn. John has 45 followers.\'

在构建一个基于模板的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。

const user = {
  name: \'John\',
  surname: \'Doe\',
  details: {
    email: \'john@doe.com\',
    displayName: \'SuperCoolJohn\',
    joined: \'2016-05-05\',
    image: \'path-to-the-image\',
    followers: 45
  }
}
const printUserInfo = (user) => { 
  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.`
  console.log(text);
}

printUserInfo(user);
// outputs \'The user is John Doe. Email: john@doe.com. Display Name: SuperCoolJohn. John has 45 followers.\'