实现36进制

function num36() {
    var arr = []
    for (let i = 0; i < 36; i++) {
        if (i < 10) {
            arr.push(i)
        } else {
            arr.push(String.fromCharCode(i + 87))
        }
    }
    return arr;
}

function trans36(n) {
    var arr = []
    var get36 = num36()
    while(n) {
        var res = n % 36;
        arr.unshift(get36[res])
        n = parseInt(n / 36)
    }
    return arr.join('')
}

手写new

function New(fn, ...args) {
    let obj = Object.create(fn.prototype);
    let res = fn.apply(obj, args)

    return typeof res === 'object' ? res : obj
}

bind

if (!Function.prototype.bind) {
    Function.prototype.bind = function() {
        let that = this
        let [ctx, ...args] = arguments
        return function() {
            that.apply(ctx, args.concat([].slice.apply(arguments)))
        }
    }
}

apply

if (!Function.prototype.apply) {
    Function.prototype.apply = function() {
        let [ctx, args] = arguments
        ctx.fn = this || window
        let res = ctx.fn(...args)
        delete ctx.fn
        return res
    }
}

call

if (!Function.prototype.call) {
    let [ctx, ...args] = arguments
    ctx.fn = this || window
    let res = ctx.fn(...args)
    delete ctx.fn
    return res
}

深复制

function deepObj(obj) {
    let newObj = {}
    Object.keys(obj).forEach((item, index) => {
        if (typeof obj[item] === 'object') {
            newObj[item] = deepObj(obj[item])
        } else {
            newObj[item] = obj[item]
        }
    })
    return newObj;
}

cookie

设置(存储object时需JSON.stringify 取出时需JSON.parse)

function setCookie(key, val, day) {
    let str = `${encodeURIComponent(key)}=${encodeURIComponent(val)}`
    if (day) {
        let date = new Date()
            date.setTime(date.getTime() + (day*24*60*60*1000))
        str += `; expires=${date.toGMTString()}`
    }
    document.cookie = str;
}

function getCookie(name) {
    let arr = document.cookie.split('; ');
    let str = ``
    arr.every((item, index) => {
        let diff = name + '=';
        if (item.indexOf(diff) === 0) {
            str = decodeURIComponent(item.replace(diff, ''))
            return false
        } else {
            return true
        }
    })
    return str
}

扁平化

1. 直接处理

[1,2,[3,4],[6,7,8,9]].flat()

2. String

String([1,2,[3,4],[6,7,8,9]]).split(',')

3. JSON.stringify

JSON.stringify([1,2,[3,4],[6,7,8,9]]).replace(/(\[|\])/g, '').split(',')

4. reduce

[1,2,[3,4],[6,7,8,9]].reduce((before, second) => {
    return before.concat(second)
}, [])

5. ...扩展运算符

[].concat(...[1,2,[3,4],[6,7,8,9]])

6. 递归

function flat(arr) {
    let newArr = []
    for (let i=0; i<arr.length; i++) {
        if (Array.isArray(arr[i])) {
            let res = flat(arr[i])
            newArr.push(...res)
        } else {
            newArr.push(arr[i])
        }
    }
    return newArr
}