# 手撕Javascript ⭐️
# 大数相加
点击查看代码
/*
* @Author: 41
* @Date: 2022-03-18 11:52:17
* @LastEditors: 41
* @LastEditTime: 2022-04-18 09:28:36
* @Description:
*/
/************************测试区域 ***************************/
let num1 = ['1002', '45646', '456465465']
let num2 = ['46', '456456', '798416132132']
let cnt = 0
for (let i = 0; i < num1.length; i++) {
if (myadd(num1[i], num2[i]) == test(num1[i], num2[i])) {
console.log(`示例${i}:TRUE`);
cnt++
} else {
console.log(`示例${i}:FALSE`);
}
}
console.log(`正确率${(cnt / num1.length) * 100}%`);
console.log(2 ** 53);
console.log(2 ** 53 + 10 - 2 ** 53);
/************************解答区域 ***************************/
/**
* @description: 大数加法BigInt
* @param1 {*}
* @return {*}
* @detail:
* @param {*} num1
* @param {*} num2
*/
function test (num1, num2) {
num1 = BigInt(num1)
num2 = BigInt(num2)
return (num1 + num2).toString()
}
/**
* @description: 手写大数加法
* @param1 {*}
* @return {*}
* @detail:
* @param {*} num1
* @param {*} num2
*/
function myadd (num1, num2) {
/*************判断输入 */
if (Object.prototype.toString.call(num1).slice(8, -1) != 'String') {
throw Error('num1 must be a string!')
}
if (Object.prototype.toString.call(num2).slice(8, -1) != 'String') {
throw Error('num2 must be a string!')
}
/**************输入处理 */
let len1 = num1.length, len2 = num2.length
if (len1 > len2) {
num2 = num2.padStart(len1, '0')
} else {
num1 = num1.padStart(len2, '0')
}
let arr1 = num1.split('').map((item) => {
return item = +item
})
let arr2 = num2.split('').map((item) => {
return item = +item
})
/***************运算处理 */
let res = [], jinwei = 0
for (let i = arr1.length - 1; i >= 0; i--) {
let temp = arr1[i] + arr2[i] + jinwei
if ((temp / 10) >> 0) {
jinwei = 1
} else {
jinwei = 0
}
res.unshift(temp % 10)
}
return res.join('');
}
# LRU
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/*
* @Author: 41
* @Date: 2022-03-10 21:24:48
* @LastEditors: 41
* @LastEditTime: 2022-03-10 21:24:49
* @Description:
*/
/**
* @param {number} capacity
*/
var LRUCache = function (capacity) {
const cache = new Map()
const max = capacity
};
/**
* @param {number} key
* @return {number}
*/
LRUCache.prototype.get = function (key) {
let map = this.cache
if (map.has(key)) {
let value = map.get(key)
map.delete(key)
map.set(key, value)
return value
} else {
return -1
}
};
/**
* @param {number} key
* @param {number} value
* @return {void}
*/
LRUCache.prototype.put = function (key, value) {
const map = this.cache
if (map.has(key)) {
map.delete(key)
}
map.set(key, value)
if (map.size > this.max) {
map.delete(map.keys().next().value)
}
};
# 比较版本号
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/*
* @Author: 41
* @Date: 2022-03-04 17:36:23
* @LastEditors: 41
* @LastEditTime: 2022-03-20 18:41:27
* @Description:
*/
/*
实现一个方法，用于比较两个版本号（version1、version2）
如果version1 > version2，返回1；
如果version1 < version2，返回-1，其他情况返回0。
版本号规则`x.y.z`，xyz均为大于等于0的整数，至少有x位
输入：compareVersion('0.1', '1.1.1')
输出：-1
输入：compareVersion('13.37', '1.2 ')
输出：1
输入：compareVersion('1.1', '1.1.0')
输出：0
*/
function compareVersion (version1, version2) {
let ver1 = version1.split('.');
let ver2 = version2.split('.');
let max = ver1.length > ver2.length ? ver1.length : ver2.length
while (ver1.length < max) {
ver1.push('0')
}
while (ver2.length < max) {
ver2.push('0')
}
// console.log(ver1, ver2);
for (let i = 0; i < ver1.length; i++) {
if (ver1[i] > ver2[i]) {
return 1
} else if (ver1[i] == ver2[i]) {
continue
} else {
return -1
}
}
return 0
}
let a = [
{ v1: "0.1", v2: "1.1.1" },
{ v1: "13.37", v2: "1.2" },
]
for (let i = 0; i < a.length; i++) {
console.log(compareVersion(a[i].v1, a[i].v2));
}
# 数字中1的个数
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/*
* @Author: 自迩
* @Date: 2022-03-06 22:36:00
* @LastEditTime: 2022-03-07 21:03:13
* @LastEditors: 41
* @Description:
* @FilePath: \面试之路\front-end-interview\javascript\bitCount.js
*/
/*************** 测试区域 *******************/
let num = 0B1100
let cnt = 0
weiyi(num, cnt) // 位移
indexdeal(num, cnt) // indexOf
splicedeal(num, cnt) // indexOf+splice
foreachdeal(num, cnt) // forEach
filterdeal(num) // filter
reducedeal(num) // reduce
/*************** 题解区域 *******************/
/**
* @description: bit移位解法
*/
function weiyi (num, cnt) {
while (num) {
if (num % 2 === 1) cnt++
num >>= 1
}
console.log(cnt);
}
/**
* @description: indexOf解法
*/
function indexdeal (num, cnt) {
let arr = num.toString(2).split('')
let index = 0
while (arr.indexOf('1', index) != -1) {
cnt++
index = arr.indexOf('1', index) + 1
}
console.log(cnt);
}
/**
* @description: indexOf+splice解法
*/
function splicedeal (num, cnt) {
let arr = num.toString(2).split('')
while (arr.indexOf('1') != -1) {
arr.splice(arr.indexOf('1'), 1)
cnt++
}
console.log(cnt);
}
/**
* @description: forEach解法
*/
function foreachdeal (num, cnt) {
let arr = num.toString(2).split('')
arr.forEach(item => {
if (item === '1') cnt++
})
console.log(cnt);
}
/**
* @description: filter解法
*/
function filterdeal (num) {
let arr = num.toString(2).split('')
let newarr = arr.filter(item => {
return item === '1'
})
console.log(newarr.length);
}
/**
* @description: reduce解法
*/
function reducedeal (num) {
let arr = num.toString(2).split('')
let res = arr.reduce((pre, cur) => {
return pre + (+cur)
}, 0)
console.log(res);
}
# 不用循环输出0到n-1的数
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/*
* @Author: 41
* @Date: 2022-03-04 17:59:10
* @LastEditors: 41
* @LastEditTime: 2022-03-17 20:58:37
* @Description:
*/
/***************测试区域 *******************/
// dfs(10)
// deal(10)
// deal2(10)
// deal3(10)
let a = Array.from(new Array(10).keys())
console.log(a);
let b = Array.from({ length: 10 }, (node, i) => i)
console.log(b);
/***************题解区域 *******************/
/**
* @description: 递归解法
*/
function dfs (x) {
let arr = []
function deal (x) {
if (x < 0) return
arr.unshift(x)
// console.log(x);
deal(x - 1)
}
deal(x - 1)
console.log(arr);
}
/**
* @description: padEnd解法
*/
function deal (x) {
let str = ''.padEnd(x, '0')
let arr = str.split('')
let cnt = 0
let res = arr.map(item => {
cnt += 1
return +item + cnt - 1
})
console.log(res);
}
/**
* @description: Array.from解法
*/
function deal2 (x) {
let arr = (new Array(x + 1)).join('0').split('')
let cnt = -1
let newarr = arr.map(item => {
cnt++
return +item + cnt
})
console.log(newarr);
}
/**
* @description: Array.fill解法
*/
function deal3 (x) {
let arr = (new Array(x)).fill('0')
let cnt = -1
let newarr = arr.map(item => {
cnt++
return +item + cnt
})
console.log(newarr);
}
# 单词统计
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/*
* @Author: 41
* @Date: 2022-03-13 15:19:19
* @LastEditors: 41
* @LastEditTime: 2022-03-13 15:32:31
* @Description:
*/
function count (article) {
article = article.trim().toUpperCase()
let array = article.match(/[A-z]+/g)
article = " " + array.join(' ') + " "
let max = 0, maxword
for (let i = 0; i < array.length; i++) {
let word = new RegExp(" " + array[i] + " ", 'g')
let num = article.match(word).length
if (num > max) {
max = num
maxword = array[i]
}
}
console.log(maxword + ' ' + max);
}
count('Age has reached the end of the beginning of a word')
# Fib数列
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/*
* @Author: 41
* @Date: 2022-04-24 17:19:11
* @LastEditors: 41
* @LastEditTime: 2022-04-26 17:43:16
* @Description:
*/
let fib = function () {
let memo = [0, 1]
let dfs = function (n) {
if (memo[n] == undefined) {
memo[n] = dfs(n - 2) + dfs(n - 1)
}
return memo[n]
}
return dfs
}()
let res = fib(10)
console.log(res);
# 全排列
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/*
* @Author: 41
* @Date: 2022-03-13 14:19:02
* @LastEditors: 41
* @LastEditTime: 2022-03-24 16:03:09
* @Description:
*/
let permute = function (nums) {
let len = nums.length, visited = new Array(len).fill(false), res = []
const dfs = (nums, len, depth, path, visited) => {
if (len == depth) {
res.push([...path])
}
for (let i = 0; i < nums.length; i++) {
if (!visited[i]) {
path.push(nums[i])
visited[i] = true
dfs(nums, len, depth + 1, path, visited)
visited[i] = false
path.pop()
}
}
}
dfs(nums, len, 0, [], visited)
return res
}
let nums = [1, 2, 3]
console.log(permute(nums));
# 生成树
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/*
* @Author: 41
* @Date: 2022-04-01 15:20:38
* @LastEditors: 41
* @LastEditTime: 2022-04-02 18:12:11
* @Description:
*/
let strarr = {
'a-b-c-d': 1,
'a-b-c-e': 2,
'a-b-f': 3,
'a-j': 4,
};
path(strarr)
function path (strarr) {
let obj = {};
Object.keys(strarr).forEach((item) => {
let reg = item.split('-')
let p = obj;
for (let i = 0; i < reg.length - 1; i++) {
let v = reg[i];
p[v] ?? (p[v] = {});
p = p[v];
}
p[reg.at(-1)] = strarr[item];
});
}
// let obj = {
// a: {
// b: {
// c: {
// d: 1,
// e: 2,
// },
// f: 3,
// },
// j: 4,
// },
// };
# 快速排序
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/*
* @Author: 41
* @Date: 2022-03-10 21:25:19
* @LastEditors: 41
* @LastEditTime: 2022-05-06 17:59:06
* @Description:
*/
/************************测试区域 */
let arr2 = [1231, 45546, 788, 12313, 1, 5, 4]
console.log(mysort2(arr2));
/************************题解区域 */
function mysort2 (arr) {
if (arr.length < 2) return arr
let target = arr.splice((arr.length / 2) >> 0, 1), left = [], right = []
arr.forEach(item => {
(item < target ? left : right).push(item)
});
return mysort2(left).concat(target, mysort2(right))
}
/***********************测试区域 */
let arr = [1231, 45546, 788, 12313, 1, 5, 4]
console.log(mysort(arr));
/************************题解区域 */
function mysort (arr) {
return quick(arr, 0, arr.length - 1)
}
function quick (arr, left, right) {
let index
if (arr.length > 1) {
index = partition(arr, left, right)
if (left < index - 1) {
quick(arr, left, index - 1)
}
if (index < right) {
quick(arr, index, right)
}
}
return arr
}
function partition (arr, left, right) {
const target = arr[left]
let i = left, j = right
while (i <= j) {
while (arr[i] < target) {
i++
}
while (arr[j] > target) {
j--
}
if (i <= j) {
[arr[i], arr[j]] = [arr[j], arr[i]]
i++
j--
}
}
return i
}
# 千分位分割
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/*
* @Author: 41
* @Date: 2022-03-18 11:37:10
* @LastEditors: 41
* @LastEditTime: 2022-04-27 19:13:10
* @Description: 实现数字的千分位逗号分割
*/
function deal (num) {
let inputArray = num.toString().split('.')
let zhengshu = inputArray[0].split('')
let xiaoshu = (inputArray.length > 1 ? inputArray[1] : '').split('')
let res1 = [], res2 = []
while (zhengshu.length) {
let temp = zhengshu.splice(-3).join('')
res1.unshift(temp)
}
while (xiaoshu.length) {
let temp = xiaoshu.splice(0, 3).join('')
res2.unshift(temp)
}
if (res2.length)
return res1.join(',') + '.' + res2.join(',')
else
return res1.join(',')
}
/***********测试区域************* */
let num = [123154.465165, 132154, 213456, 12.123456, 123145.1231]
for (let i = 0; i < num.length; i++) {
console.log(deal(num[i]))
}
# 隔一秒输出数字
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/*
* @Author: 41
* @Date: 2022-03-18 11:20:31
* @LastEditors: 41
* @LastEditTime: 2022-03-18 11:27:15
* @Description:
*/
const oneToThree = () => {
const arr = [1, 2, 3];
arr.reduce((prev, next) => {
return prev.then(() => {
return new Promise((resolve) => {
setTimeout(() => {
console.log(next);
resolve();
}, 1000);
})
});
}, Promise.resolve())
};
// oneToThree();
for (let i = 0; i < 3; i++) {
setTimeout(() => {
console.log(i + 1);
}, (i + 1) * 1000)
}
# 柯里化
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/*
* @Author: 41
* @Date: 2022-03-13 15:39:04
* @LastEditors: 41
* @LastEditTime: 2022-04-18 20:15:54
* @Description:
*/
/**
* 将函数柯里化
* @param fn 待柯里化的原函数
* @param len 所需的参数个数，默认为原函数的形参个数
*/
function curry (fn, len = fn.length) {
return _curry.call(this, fn, len)
}
/**
* 中转函数
* @param fn 待柯里化的原函数
* @param len 所需的参数个数
* @param args 已接收的参数列表
*/
function _curry (fn, len, ...args) {
return function (...params) {
let _args = [...args, ...params];
if (_args.length >= len) {
return fn.apply(this, _args);
} else {
return _curry.call(this, fn, len, ..._args)
}
}
}
function fn (a, b, c, d) {
console.log(a, b, c, d);
}
// let _fn = curry(fn)
// _fn(1, 2, 3, 4)
// _fn(1)(2, 3)(4)
/************************************* */
function add () {
let args = [...arguments]
let inner = function () {
args.push(...arguments)
return inner
}
inner.toString = function () {
return args.reduce((pre, cur) => {
return pre * cur
})
}
return inner
}
const res = add(1)(2)(3)(4)(5).toString()
console.log(res);
# ObjFlat拍平
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/*
* @Author: 41
* @Date: 2022-03-31 14:24:11
* @LastEditors: 41
* @LastEditTime: 2022-04-22 14:56:44
* @Description:
*/
/***********************测试区域 */
let obj = {
name: {
value: 41,
a: 1,
b: 2
},
age: {
value: 20
},
other: {
hobby: {
music1: 'guita',
music2: 'sing'
}
}
}
let res = myFlat(obj)
console.log(res);
/***********************题解区域 */
function myFlat (obj) {
let newobj = {}
function dfs (obj, path) {
if (Object.prototype.toString.call(obj).slice(8, -1) !== 'Object') {
newobj[path] = obj
} else {
for (let key in obj) {
if (obj.hasOwnProperty(key)) {
if (path) dfs(obj[key], path + '-' + key)
else dfs(obj[key], key)
}
}
}
}
dfs(obj, '')
return newobj
}
# lodashGet
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/*
* @Author: 41
* @Date: 2022-04-24 17:09:02
* @LastEditors: 41
* @LastEditTime: 2022-04-24 17:17:50
* @Description:
*/
function get (object, path, defaultVal = 'undefined') {
let newPath = []
if (Array.isArray(path)) {
newPath = path
} else {
// console.log(path);
newPath = path.replace(/\[/g, '.').replace(/\]/g, '').split('.')
// console.log(newPath);
}
return newPath.reduce((o, k) => {
// console.log(o, k);
return (o || {})[k]
}, object) || defaultVal
}
var object = { 'a': [{ 'b': { 'c': 3 } }] };
console.log(get(object, 'a[0].b.c'));
# DeepClone
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/*
* @Author: 41
* @Date: 2022-03-16 11:24:48
* @LastEditors: 41
* @LastEditTime: 2022-03-24 11:19:47
* @Description:
*/
function getType (obj) {
return Object.prototype.toString.call(obj).slice(8, -1)
}
function deepClone (obj, map = new WeakMap()) {
if (obj === null) return obj
if (getType(obj) === 'RegExp') return new RegExp(obj)
if (getType(obj) === 'Date') return new Date(obj)
if (getType(obj) !== 'Object' && getType(obj) !== 'Array') return obj
if (map.has(obj)) return map.get(obj)
let cloneobj = getType(obj) === 'Array' ? [] : {}
map.set(obj, cloneobj)
for (let key in obj) {
if (obj.hasOwnProperty(key)) {
cloneobj[key] = deepClone(obj[key], map)
}
}
return cloneobj
}
let obj = {
name: 41,
arr: [1, { test: 123 }, 3, 4, 5],
haha: {
name: 123
}
}
let newobj = deepClone(obj)
obj.name = 42
obj.arr[0] = 5
obj.arr[1].test = 5
obj.haha.name = 5
console.log(obj, newobj);
# 手写reduce
点击查看代码
/*
* @Author: 自迩
* @Date: 2022-03-06 22:22:51
* @LastEditTime: 2022-03-24 16:45:33
* @LastEditors: 41
* @Description:
* @FilePath: \面试之路\front-end-interview\javascript\myreduce.js
*/
/*************题解区域 *********************/
Array.prototype.myReduce = function (fn, init) {
if (Object.prototype.toString.call(fn).slice(8, -1) !== 'Function') {
throw error('first parameter must be Function')
}
let arr = this
let pre = init
let index = 0
if (!init) {
pre = arr[index]
index++
}
for (let i = index; i < arr.length; i++) {
pre = fn(pre, arr[i], i, arr)
}
return pre
}
/*************测试区域 *********************/
let arr = [1, 2, 3]
let result = arr.myReduce((pre, cur) => {
return pre + cur
}, 0)
console.log(result);
# 手写repeat
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/*
* @Author: 41
* @Date: 2022-03-07 21:41:51
* @LastEditors: 41
* @LastEditTime: 2022-03-07 21:51:27
* @Description:
*/
console.log(repeat('123', 2));
console.log(repeat2('123', 2));
console.log(repeat3('123', 2));
/**
* @description: 1.空数组join
*/
function repeat (target, n) {
return (new Array(n + 1)).join(target)
}
/**
* @description: 2.省去创建数组
*/
function repeat2 (target, n) {
return Array.prototype.join.call({
length: n + 1
}, target)
}
/**
* @description:
*/
function repeat3 (target, n) {
let res = ''
while (n--) {
res += target
}
return res
}
# 手写Promise
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/*
* @Author: 41
* @Date: 2022-04-06 11:31:29
* @LastEditors: 41
* @LastEditTime: 2022-04-06 17:40:19
* @Description:
*/
class Commitment {
static PENDING = '待定'
static FULFILED = '成功'
static REJECTED = '拒绝'
constructor(func) {
this.status = Commitment.PENDING
this.result = null
this.resolveCallbacks = []
this.rejectCallbacks = []
// func(this.resolve.bind(this), this.reject.bind(this))
try {
func(this.resolve.bind(this), this.reject.bind(this))
} catch (error) {
this.reject(error)
}
}
resolve (result) {
setTimeout(() => {
if (this.status === Commitment.PENDING) {
this.status = Commitment.FULFILED
this.result = result
this.resolveCallbacks.forEach(callback => {
callback(result)
})
}
})
}
reject (result) {
setTimeout(() => {
if (this.status === Commitment.PENDING) {
this.status = Commitment.REJECTED
this.result = result
this.rejectCallbacks.forEach(callback => {
callback(result)
})
}
});
}
then (onFULFILED, onREJECTED) {
return new Commitment((resolve, reject) => {
onFULFILED = typeof onFULFILED === 'function' ? onFULFILED : () => { }
onREJECTED = typeof onREJECTED === 'function' ? onREJECTED : () => { }
if (this.status === Commitment.PENDING) {
this.resolveCallbacks.push(onFULFILED)
this.rejectCallbacks.push(onREJECTED)
}
if (this.status === Commitment.FULFILED) {
setTimeout(() => {
onFULFILED(this.result)
})
}
if (this.status === Commitment.REJECTED) {
setTimeout(() => {
onREJECTED(this.result)
})
}
})
}
}
let commitment = new Commitment((res, rej) => {
res('这次一定')
})
commitment.then(
result => { console.log(result); },
result => { console.log(result.message); }
).then(
result => { console.log(result); },
result => { console.log(result.message); }
)
# 手写Promise.all
点击查看代码
/*
* @Author: 41
* @Date: 2022-03-18 11:28:35
* @LastEditors: 41
* @LastEditTime: 2022-05-06 17:56:32
* @Description:
*/
Promise.myAll = function (promiseArr) {
return new Promise((resolve, reject) => {
const ans = []
let index = 0
for (let i = 0; i < promiseArr.length; i++) {
promiseArr[i]
.then(res => {
ans[i] = res
index++
if (index === promiseArr.length) {
this.resolve(ans)
}
})
.catch(err => reject(err))
}
})
}