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。
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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。
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:
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 }
8.字符串插值
在用例中,如果正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.'
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