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  • 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.'
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  • 原文地址:https://www.cnblogs.com/art-poet/p/12070598.html
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