JS中可能会常用到的一些数据处理方法

DOM处理
  1. 检查一个元素是否被聚焦
const hasFocus = ele => (ele === document.activeElement);
  1. 检查用户是否滚动到页面底部
const isAtBottom = () => document.documentElement.clientHeight + window.scrollY >= document.documentElement.scrollHeight;
  1. 获取一个元素的所有兄弟元素
const siblings = ele => [].slice.call(ele.parentNode.children).filter((child) => (child !== ele));
  1. 获取元素相对于文档的位置
const getPosition = ele => (r = ele.getBoundingClientRect(), { 
left: r.left + window.scrollX, top: r.top + window.scrollY
 });

// Example
getPosition(document.body);     // { left: 0, top: 0 }
  1. 在另一个元素之后插入一个元素
const insertAfter = (ele, anotherEle) => anotherEle.parentNode.insertBefore(ele, anotherEle.nextSibling);

// Or
const insertAfter = (ele, anotherEle) => anotherEle.insertAdjacentElement('afterend', ele);

附:在其他元素之前插入一个元素

const insertBefore = (ele, anotherEle) => anotherEle.parentNode.insertBefore(ele, anotherEle);

// Or
const insertBefore = (ele, anotherEle) => anotherEle.insertAdjacentElement('beforebegin', ele);
  1. 在元素后面插入给定的 HTML
const insertHtmlAfter = (html, ele) => ele.insertAdjacentHTML('afterend', html);

附:在元素之前插入给定的 HTML

const insertHtmlBefore = (html, ele) => ele.insertAdjacentHTML('beforebegin', html);
  1. 滚动到页面顶部(返回顶部)
const goToTop = () => window.scrollTo(, );
数组
  1. 数组判空
// `arr` is an array
const isEmpty = arr => !Array.isArray(arr) || arr.length === ;

// Examples
isEmpty([]);            // true
isEmpty([1, 2, 3]);     // false
  1. 克隆数组
// `arr` is an array
const clone = arr => arr.slice();

// Or
const clone = arr => [...arr];

// Or
const clone = arr => Array.from(arr);

// Or
const clone = arr => arr.map(x => x);

// Or
const clone = arr => JSON.parse(JSON.stringify(arr));

// Or
const clone = arr => arr.concat([]);
  1. 找到数组中最大值对应的索引
const indexOfMax = arr => arr.reduce((prev, curr, i, a) => curr > a[prev] ? i : prev, );

// Examples
indexOfMax([1, 3, 9, 7, 5]);        // 2
indexOfMax([1, 3, 7, 7, 5]);        // 2

附:最小值对应的索引

const indexOfMin = arr => arr.reduce((prev, curr, i, a) => curr < a[prev] ? i : prev, );

// Examples
indexOfMin([6, 4, 8, 2, 10]);       // 3
indexOfMin([6, 4, 2, 2, 10]);       // 2
  1. 获取数组的交集
const getIntersection = (a, ...arr) => [...new Set(a)].filter(v => arr.every(b => b.includes(v)));

// Examples
getIntersection([1, 2, 3], [2, 3, 4, 5]);               // [2, 3]
getIntersection([1, 2, 3], [2, 3, 4, 5], [1, 3, 5]);    // [3]
  1. 按键对一组对象进行分组
const groupBy = (arr, key) => arr.reduce((acc, item) => ((acc[item[key]] = [...(acc[item[key]] || []), item]), acc), {});

// Example
groupBy([
    { branch: 'audi', model: 'q8', year: '2019' },
    { branch: 'audi', model: 'rs7', year: '2020' },
    { branch: 'ford', model: 'mustang', year: '2019' },
    { branch: 'ford', model: 'explorer', year: '2020' },
    { branch: 'bmw', model: 'x7', year: '2020' },
], 'branch');

/*
{
    audi: [
        { branch: 'audi', model: 'q8', year: '2019' },
        { branch: 'audi', model: 'rs7', year: '2020' }
    ],
    bmw: [
        { branch: 'bmw', model: 'x7', year: '2020' }
    ],
    ford: [
        { branch: 'ford', model: 'mustang', year: '2019' },
        { branch: 'ford', model: 'explorer', year: '2020' }
    ],
}
*/
  1. 删除数组中的重复值
const removeDuplicate = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));

// Example
removeDuplicate(['h', 'e', 'l', 'l', 'o', 'w', 'o', 'r', 'l', 'd']); //  ['h', 'e', 'w', 'r', 'd']
  1. 按给定的键对数组中的项进行排序
const sortBy = (arr, k) => arr.concat().sort((a, b) => (a[k] > b[k]) ? 1 : ((a[k] < b[k]) ? -1 : ));

// Example
const people = [
    { name: 'Foo', age: 42 },
    { name: 'Bar', age: 24 },
    { name: 'Fuzz', age: 36 },
    { name: 'Baz', age: 32 },
];
sortBy(people, 'age');

// returns
//  [
//      { name: 'Bar', age: 24 },
//      { name: 'Baz', age: 32 },
//      { name: 'Fuzz', age: 36 },
//      { name: 'Foo', age: 42 },
//  ]
方法

将 URL 参数转换为对象

const getUrlParams = query => Array.from(new URLSearchParams(query)).reduce((p, [k, v]) => Object.assign({}, p, { [k]: p[k] ? (Array.isArray(p[k]) ? p[k] : [p[k]]).concat(v) : v}), {});

// Examples
getUrlParams(location.search);              // Get the parameters of the current URL

getUrlParams('foo=Foo&bar=Bar');            // { foo: "Foo", bar: "Bar" }

// Duplicate key
getUrlParams('foo=Foo&foo=Fuzz&bar=Bar');   // { foo: ["Foo", "Fuzz"], bar: "Bar" }

从 URL 获取参数的值

const getParam = (url, param) => new URLSearchParams(new URL(url).search).get(param);

// Example
getParam('http://domain.com?message=hello', 'message');     // 'hello'

用零作为整数的前缀

const prefixWithZeros = (number, length) => (number / Math.pow(10, length)).toFixed(length).substr(2);

// Or
const prefixWithZeros = (number, length) => `${Array(length).join('0')}${number}`.slice(-length);

// Or
const prefixWithZeros = (number, length) => String(number).padStart(length, '0');

// Example
prefixWithZeros(42, 5);     // '00042'

将数字四舍五入到给定的数字位数

const prefixWithZeros = (number, length) => (number / Math.pow(10, length)).toFixed(length).substr(2);

// Or
const prefixWithZeros = (number, length) => `${Array(length).join('0')}${number}`.slice(-length);

// Or
const prefixWithZeros = (number, length) => String(number).padStart(length, '0');

// Example
prefixWithZeros(42, 5);     // '00042'

将一个数字截断为给定的小数位数而不进行舍入

const toFixed = (n, fixed) => `${n}`.match(new RegExp(`^-?\\d+(?:\.\\d{0,${fixed}})?`))[];

// Or
const toFixed = (n, fixed) => ~~(Math.pow(10, fixed) * n) / Math.pow(10, fixed);

// Examples
toFixed(25.198726354, 1);       // 25.1
toFixed(25.198726354, 2);       // 25.19
toFixed(25.198726354, 3);       // 25.198
toFixed(25.198726354, 4);       // 25.1987
toFixed(25.198726354, 5);       // 25.19872
toFixed(25.198726354, 6);       // 25.198726

从对象中移除所有 null 和未定义的属性

const removeNullUndefined = obj => Object.entries(obj).reduce((a, [k, v]) => (v == null ? a : (a[k] = v, a)), {});

// Or
const removeNullUndefined = obj => Object.entries(obj).filter(([_, v]) => v != null).reduce((acc, [k, v]) => ({ ...acc, [k]: v }), {});

// Or
const removeNullUndefined = obj => Object.fromEntries(Object.entries(obj).filter(([_, v]) => v != null));

// Example
removeNullUndefined({
    foo: null,
    bar: undefined,
    fuzz: 42,
});

检查字符串是否为回文

const isPalindrome = str => str === str.split('').reverse().join('');

// Examples
isPalindrome('abc');        // false
isPalindrom('abcba');       // true

将一个字符串转换为 camelCase

const toCamelCase = str => str.trim().replace(/[-_\s]+(.)?/g, (_, c) => c ? c.toUpperCase() : '');

// Examples
toCamelCase('background-color');            // backgroundColor
toCamelCase('-webkit-scrollbar-thumb');     // WebkitScrollbarThumb
toCamelCase('_hello_world');                // HelloWorld
toCamelCase('hello_world');                 // helloWorld

将字符串转换为 PascalCase

const toPascalCase = str => (str.match(/[a-zA-Z0-9]+/g) || []).map(w => `${w.charAt().toUpperCase()}${w.slice(1)}`).join('');

// Examples
toPascalCase('hello world');    // 'HelloWorld'
toPascalCase('hello.world');    // 'HelloWorld'
toPascalCase('foo_bar-baz');    // FooBarBaz

转义 HTML 特殊字符

const escape = str => str.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/'/g, '&#39;').replace(/"/g, '&quot;');

// Or
const escape = str => str.replace(/[&<>"']/g, m => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' })[m]);

将多个空格替换为单个空格

// Replace spaces, tabs and new line characters
const replaceSpaces = str => str.replace(/\s\s+/g, ' ');

// Only replace spaces
const replaceOnlySpaces = str => str.replace(/  +/g, ' ');

// Example
replaceSpaces('this\n   is     \ta    \rmessage');  // 'this is a message'

在字母顺序中对文本文档的行进行排序

const sortLines = str => str.split(/\r?\n/).sort().join('\n');

// Reverse the order
const reverseSortedLines = str => str.split(/\r?\n/).sort().reverse().join('\n');

// Example
sortLines(`Thaddeus Mullen
Kareem Marshall
Ferdinand Valentine
Hasad Lindsay
Mufutau Berg
Knox Tyson
Kasimir Fletcher
Colton Sharp
Adrian Rosales
Theodore Rogers`);

/* Output */
/*
Adrian Rosales
Colton Sharp
Ferdinand Valentine
Hasad Lindsay
Kareem Marshall
Kasimir Fletcher
Knox Tyson
Mufutau Berg
Thaddeus Mullen
Theodore Rogers
*/

将字符串截断为完整的单词(超出隐藏)

const truncate = (str, max, suffix) => str.length < max ? str : `${str.substr(, str.substr(, max - suffix.length).lastIndexOf(' '))}${suffix}`;

// Example
truncate('This is a long message', 20, '...');  // 'This is a long...'

取消转义 HTML 特殊字符

const unescape = str => str.replace(/&amp;/g , '&').replace(/&lt;/g  , '<').replace(/&gt;/g  , '>').replace(/�*39;/g , "'").replace(/&quot;/g, '"');
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