DOM处理
DOM 为文档提供了结构化表示，并定义了如何通过脚本来访问文档结构。目的其实就是为了能让js操作html元素而制定的一个规范。DOM就是由节点组成的。
检查一个元素是否被聚焦
const hasFocus = ele => (ele === document.activeElement);
检查用户是否滚动到页面底部
const isAtBottom = () => document.documentElement.clientHeight + window.scrollY >= document.documentElement.scrollHeight;
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));
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 }
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);
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);
滚动到页面顶部（返回顶部）
const goToTop = () => window.scrollTo(0, 0);
数组
数组判空
// `arr` is an array
const isEmpty = arr => !Array.isArray(arr) || arr.length === 0;
// Examples
isEmpty([]); // true
isEmpty([1, 2, 3]); // false
克隆数组
// `arr` is an array
const clone = arr => arr.slice(0);
// 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([]);
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, 0);
// 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, 0);
// Examples
indexOfMin([6, 4, 8, 2, 10]); // 3
indexOfMin([6, 4, 2, 2, 10]); // 2
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]
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');
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']
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 : 0));
// 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}})?`))[0];
// 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 => `${w.charAt(0).toUpperCase()}${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, '&').replace(/</g, '<').replace(/>/g, '>').replace(/'/g, ''').replace(/"/g, '"');
// Or
const escape = str => str.replace(/[&<>"']/g, m => ({ '&': '&', '<': '<', '>': '>', '"': '"', "'": ''' })[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`);
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 : `${str.substr(0, str.substr(0, max - suffix.length).lastIndexOf(' '))}${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(/&/g , '&').replace(/</g , '<').replace(/>/g , '>').replace(/�*39;/g , "'").replace(/"/g, '"');
总结
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