269个JavaScript工具函数，助你提升工作效率（7）

181.如何在等待指定时间后调用提供的函数？

const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);
 delay(
   function(text) {
     console.log(text);
   },
   1000,
   'later'
 ); 

 // 1秒后打印 'later'

182.如何在给定元素上触发特定事件且能选择地传递自定义数据？

const triggerEvent = (el, eventType, detail) =>
   el.dispatchEvent(new CustomEvent(eventType, { detail }));

 // 事例
 triggerEvent(document.getElementById('myId'), 'click');
 triggerEvent(document.getElementById('myId'), 'click', { username: 'bob' });
自定义事件的函数有 Event、CustomEvent 和 dispatchEvent
 // 向 window派发一个resize内置事件
 window.dispatchEvent(new Event('resize'))


 // 直接自定义事件，使用 Event 构造函数：
 var event = new Event('build');
 var elem = document.querySelector('#id')
 // 监听事件
 elem.addEventListener('build', function (e) { ... }, false);
 // 触发事件.
 elem.dispatchEvent(event);
CustomEvent 可以创建一个更高度自定义事件，还可以附带一些数据，具体用法如下：
 var myEvent = new CustomEvent(eventname, options);
 其中 options 可以是：
 {
   detail: {
     ...
   },
   bubbles: true,    //是否冒泡
   cancelable: false //是否取消默认事件
 }
其中 detail 可以存放一些初始化的信息，可以在触发的时候调用。其他属性就是定义该事件是否具有冒泡等等功能。
 内置的事件会由浏览器根据某些操作进行触发，自定义的事件就需要人工触发。
 dispatchEvent 函数就是用来触发某个事件：
 element.dispatchEvent(customEvent);

 上面代码表示，在 element 上面触发 customEvent 这个事件。
 // add an appropriate event listener
 obj.addEventListener("cat", function(e) { process(e.detail) });

 // create and dispatch the event
 var event = new CustomEvent("cat", {"detail":{"hazcheeseburger":true}});
 obj.dispatchEvent(event);
 使用自定义事件需要注意兼容性问题，而使用 jQuery 就简单多了：

 // 绑定自定义事件
 $(element).on('myCustomEvent', function(){});

 // 触发事件
 $(element).trigger('myCustomEvent');
 // 此外，你还可以在触发自定义事件时传递更多参数信息：

 $( "p" ).on( "myCustomEvent", function( event, myName ) {
   $( this ).text( myName + ", hi there!" );
 });
 $( "button" ).click(function () {
   $( "p" ).trigger( "myCustomEvent", [ "John" ] );
 });

183.如何从元素中移除事件监听器?

const off = (el, evt, fn, opts = false) => el.removeEventListener(evt, fn, opts);

 const fn = () => console.log('!');
 document.body.addEventListener('click', fn);
 off(document.body, 'click', fn); 

184.如何获得给定毫秒数的可读格式？

const formatDuration = ms => {
   if (ms < 0) ms = -ms;
   const time = {
     day: Math.floor(ms / 86400000),
     hour: Math.floor(ms / 3600000) % 24,
     minute: Math.floor(ms / 60000) % 60,
     second: Math.floor(ms / 1000) % 60,
     millisecond: Math.floor(ms) % 1000
   };
   return Object.entries(time)
     .filter(val => val[1] !== 0)
     .map(([key, val]) => `${val} ${key}${val !== 1 ? 's' : ''}`)
     .join(', ');
 };

 // 事例
 formatDuration(1001); // '1 second, 1 millisecond'
 formatDuration(34325055574); 
 // '397 days, 6 hours, 44 minutes, 15 seconds, 574 milliseconds'

185.如何获得两个日期之间的差异（以天为单位）？

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
   (dateFinal - dateInitial) / (1000 * 3600 * 24);

 // 事例
 getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9

186.如何向传递的URL发出GET请求？

const httpGet = (url, callback, err = console.error) => {
   const request = new XMLHttpRequest();
   request.open('GET', url, true);
   request.onload = () => callback(request.responseText);
   request.onerror = () => err(request);
   request.send();
 };

 httpGet(
   'https://jsonplaceholder.typicode.com/posts/1',
   console.log
 ); 

 // {"userId": 1, "id": 1, "title": "sample title", "body": "my text"}

187.如何对传递的URL发出POST请求？

const httpPost = (url, data, callback, err = console.error) => {
   const request = new XMLHttpRequest();
   request.open('POST', url, true);
   request.setRequestHeader('Content-type', 'application/json; charset=utf-8');
   request.onload = () => callback(request.responseText);
   request.onerror = () => err(request);
   request.send(data);
 };

 const newPost = {
   userId: 1,
   id: 1337,
   title: 'Foo',
   body: 'bar bar bar'
 };
 const data = JSON.stringify(newPost);
 httpPost(
   'https://jsonplaceholder.typicode.com/posts',
   data,
   console.log
 ); 

 // {"userId": 1, "id": 1337, "title": "Foo", "body": "bar bar bar"}

188.如何为指定选择器创建具有指定范围，步长和持续时间的计数器？

const counter = (selector, start, end, step = 1, duration = 2000) => {
   let current = start,
     _step = (end - start) * step < 0 ? -step : step,
     timer = setInterval(() => {
       current += _step;
       document.querySelector(selector).innerHTML = current;
       if (current >= end) document.querySelector(selector).innerHTML = end;
       if (current >= end) clearInterval(timer);
     }, Math.abs(Math.floor(duration / (end - start))));
   return timer;
 };

 // 事例
 counter('#my-id', 1, 1000, 5, 2000); 
 // 让 `id=“my-id”`的元素创建一个2秒计时器

189.如何将字符串复制到剪贴板？

const el = document.createElement('textarea');
   el.value = str;
   el.setAttribute('readonly', '');
   el.style.position = 'absolute';
   el.style.left = '-9999px';
   document.body.appendChild(el);
   const selected =
     document.getSelection().rangeCount > 0 ? document.getSelection().getRangeAt(0) : false;
   el.select();
   document.execCommand('copy');
   document.body.removeChild(el);
   if (selected) {
     document.getSelection().removeAllRanges();
     document.getSelection().addRange(selected);
   }
 };

 // 事例
 copyToClipboard('Lorem ipsum'); 
 // 'Lorem ipsum' copied to clipboard

190.如何确定页面的浏览器选项卡是否聚焦？

const isBrowserTabFocused = () => !document.hidden;

 // 事例
 isBrowserTabFocused(); // true

191.如何创建目录（如果不存在）？

const fs = require('fs');
 const createDirIfNotExists = dir => (!fs.existsSync(dir) ? fs.mkdirSync(dir) : undefined);

 // 事例
 createDirIfNotExists('test'); 
这里面的方法大都挺实用，可以解决很多开发过程问题，大家就好好利用起来吧。

192.日期型函数封装

function formatTime(date) {
  if(!!date){
    if(!(date instanceof Date))
    date = new Date(date);
    var month = date.getMonth() + 1
    var day = date.getDate()
    return `${month}月${day}日`;
  }
}

function formatDay(date) {
  if(!!date){
    var year = date.getFullYear()
    var month = date.getMonth() + 1
    var day = date.getDate()
    return [year, month, day].map(formatNumber).join('-');
  }
}

function formatDay2(date) {
  if(!!date){
    var year = date.getFullYear()
    var month = date.getMonth() + 1
    var day = date.getDate()
    return [year, month, day].map(formatNumber).join('/');
  }
}

function formatWeek(date){
  if(!!date){
    var day = date.getDay();
    switch (day) {
      case 0:
        return '周日'
        break;
      case 1:
        return '周一'
        break;
      case 2:
        return '周二'
        break;
      case 3:
        return '周三'
        break;
      case 4:
        return '周四'
        break;
      case 5:
        return '周五'
        break;
      case 6:
        return '周六'
        break;
    }
  }
}

function formatHour(date){
  if(!!date){
    var hour = new Date(date).getHours();
    var minute = new Date(date).getMinutes();
    return [hour, minute].map(formatNumber).join(':');
  }
}

function timestamp(date, divisor=1000){
  if(date == undefined){
    return;
  }else if(typeof date == 'number'){
    return Math.floor(date/divisor);
  }else if(typeof date == 'string'){
    var strs = date.split(/[^0-9]/);
    return Math.floor(+new Date(strs[0] || 0,(strs[1] || 0)-1,strs[2] || 0,strs[3] || 0,strs[4] || 0,strs[5] || 0)/divisor);
  }else if(Date.prototype.isPrototypeOf(date)){
    return Math.floor(+date/divisor);
  }
}

function detimestamp(date){
  if(!!date){
    return new Date(date*1000);
  }
}

function formatNumber(n) {//给在0-9的日期加上0
  n = n.toString()
  return n[1] ? n : '0' + n
}

module.exports = {
  formatTime: formatTime,
  formatDay: formatDay,
  formatDay2: formatDay2,
  formatHour: formatHour,
  formatWeek: formatWeek,
  timestamp: timestamp,
  detimestamp: detimestamp
}

193.时间戳转时间

/** 
 * 时间戳转化为年 月 日 时 分 秒 
 * number: 传入时间戳 
 * format：返回格式，支持自定义，但参数必须与formateArr里保持一致 
*/  
function formatTime(number,format) {  
  
  var formateArr  = ['Y','M','D','h','m','s'];  
  var returnArr   = [];  
  
  var date = new Date(number * 1000);  
  returnArr.push(date.getFullYear());  
  returnArr.push(formatNumber(date.getMonth() + 1));  
  returnArr.push(formatNumber(date.getDate()));  
  
  returnArr.push(formatNumber(date.getHours()));  
  returnArr.push(formatNumber(date.getMinutes()));  
  returnArr.push(formatNumber(date.getSeconds()));  
  
  for (var i in returnArr)  
  {  
    format = format.replace(formateArr[i], returnArr[i]);  
  }  
  return format;  
} 

//数据转化  
function formatNumber(n) {  
  n = n.toString()  
  return n[1] ? n : '0' + n  
}  

调用示例：

var sjc = 1488481383;//时间戳
console.log(time.formatTime(sjc,'Y/M/D h:m:s'));//转换为日期：2017/03/03 03:03:03
console.log(time.formatTime(sjc, 'h:m'));//转换为日期：03:03

194.js中获取上下文路径

js中获取上下文路径
    //js获取项目根路径，如： http://localhost:8083/uimcardprj
    function getRootPath(){
        //获取当前网址，如： http://localhost:8083/uimcardprj/share/meun.jsp
        var curWwwPath=window.document.location.href;
        //获取主机地址之后的目录，如： uimcardprj/share/meun.jsp
        var pathName=window.document.location.pathname;
        var pos=curWwwPath.indexOf(pathName);
        //获取主机地址，如： http://localhost:8083
        var localhostPaht=curWwwPath.substring(0,pos);
        //获取带"/"的项目名，如：/uimcardprj
        var projectName=pathName.substring(0,pathName.substr(1).indexOf('/')+1);
        return(localhostPaht+projectName);
    }

195.JS大小转化B KB MB GB的转化方法

function conver(limit){  
            var size = "";  
            if( limit < 0.1 * 1024 ){ //如果小于0.1KB转化成B  
                size = limit.toFixed(2) + "B";    
            }else if(limit < 0.1 * 1024 * 1024 ){//如果小于0.1MB转化成KB  
                size = (limit / 1024).toFixed(2) + "KB";              
            }else if(limit < 0.1 * 1024 * 1024 * 1024){ //如果小于0.1GB转化成MB  
                size = (limit / (1024 * 1024)).toFixed(2) + "MB";  
            }else{ //其他转化成GB  
                size = (limit / (1024 * 1024 * 1024)).toFixed(2) + "GB";  
            }  
              
            var sizestr = size + "";   
            var len = sizestr.indexOf("\.");  
            var dec = sizestr.substr(len + 1, 2);  
            if(dec == "00"){//当小数点后为00时 去掉小数部分  
                return sizestr.substring(0,len) + sizestr.substr(len + 3,2);  
            }  
            return sizestr;  
}  

196.js全屏和退出全屏

function fullScreen() {
      var el = document.documentElement;
      var rfs = el.requestFullScreen || el.webkitRequestFullScreen || el.mozRequestFullScreen || el.msRequestFullScreen;

​      //typeof rfs != "undefined" && rfs
​      if (rfs) {
​        rfs.call(el);
​      } else if (typeof window.ActiveXObject !== "undefined") {
​        //for IE，这里其实就是模拟了按下键盘的F11，使浏览器全屏
​        var wscript = new ActiveXObject("WScript.Shell");
​        if (wscript != null) {
​          wscript.SendKeys("{F11}");
​        }
​      }
​    }

​    //退出全屏
​    function exitScreen() {
​      var el = document;
​      var cfs = el.cancelFullScreen || el.webkitCancelFullScreen || el.mozCancelFullScreen || el.exitFullScreen;

​      //typeof cfs != "undefined" && cfs
​      if (cfs) {
​        cfs.call(el);
​      } else if (typeof window.ActiveXObject !== "undefined") {
​        //for IE，这里和fullScreen相同，模拟按下F11键退出全屏
​        var wscript = new ActiveXObject("WScript.Shell");
​        if (wscript != null) {
​          wscript.SendKeys("{F11}");
​        }
​      }
​    }

197.格式化时间，转化为几分钟前，几秒钟前

 /**
     * 格式化时间，转化为几分钟前，几秒钟前
     * @param timestamp 时间戳，单位是毫秒
     */
    function timeFormat(timestamp) {
        var mistiming = Math.round((Date.now() - timestamp) / 1000);
        var arrr = ['年', '个月', '星期', '天', '小时', '分钟', '秒'];
        var arrn = [31536000, 2592000, 604800, 86400, 3600, 60, 1];
        for (var i = 0; i < arrn.length; i++) {
            var inm = Math.floor(mistiming / arrn[i]);
            if (inm != 0) {
                return inm + arrr[i] + '前';
            }
        }
    }

198 获取n天之前的日期 getDaysBeforeDate(10) 10天前

/**
     * 获取n天之前的日期 getDaysBeforeDate(10) 10天前
     * @param day 天数
     */
    function getDaysBeforeDate(day) {
        var date = new Date(),
            timestamp, newDate;
        timestamp = date.getTime();
        // 获取三天前的日期
        newDate = new Date(timestamp - day * 24 * 3600 * 1000);
        var year = newDate.getFullYear();
        // 月+1是因为js中月份是按0开始的
        var month = newDate.getMonth() + 1;
        var day = newDate.getDate();
        if (day < 10) { // 如果日小于10，前面拼接0
            day = '0' + day;
        }
        if (month < 10) { // 如果月小于10，前面拼接0
            month = '0' + month;
        }
        return [year, month, day].join('/');
    }

199.获取跳转的classId,通过hash方式获取

 /**
     * 获取跳转的classId,通过hash方式获取
     * @return 返回值
     */

    $scope.getQueryString = function() {
        var url= {},
            a = '';
        (a = window.location.search.substr(1)) || (a = window.location.hash.split('?')[1])
        a.split(/&/g).forEach(function(item) {
            url[(item = item.split('='))[0]] = item[1];
        })
        return url
    }

200.过滤器指定字段

function filterArrBySex(data, name) {
        if (!name) {
            console.log(name)
            return data;
        } else {
            return data.filter(function(ele, index, self) {
                if (ele.name.includes(name)) {
                    return ele
                }
            })
        }
    }

201.根据身份证获取出生年月

 /**
     * 根据身份证获取出生年月
     * @param idCard
     */
    function getBirthdayFromIdCard(idCard) {
        var birthday = "";
        if (idCard != null && idCard != "") {
            if (idCard.length == 15) {
                birthday = "19" + idCard.substr(6, 6);
            } else if (idCard.length == 18) {
                birthday = idCard.substr(6, 8);
            }

            birthday = birthday.replace(/(.{4})(.{2})/, "$1-$2-");
        }

        return birthday;
    }

202.根据身份证获取年龄

/**
     * 根据身份证获取年龄
     * @param UUserCard
     */
    function IdCard(UUserCard) {
        //获取年龄
        var myDate = new Date();
        var month = myDate.getMonth() + 1;
        var day = myDate.getDate();
        var age = myDate.getFullYear() - UUserCard.substring(6, 10) - 1;
        if (UUserCard.substring(10, 12) < month || UUserCard.substring(10, 12) == month && UUserCard.substring(12, 14) <= day) {
            age++;
        }
        return age
    }


//vue购物车金额结算
window.onload = function() {
    var vm = new Vue({
        el: '#app',
        data: {
            items: [{
                    id: 1,
                    name: "苹果",
                    price: 10,
                    count: 1,
                    url: "http://www.jq22.com/img/cs/500x500-1.png"
                },
                {
                    id: 2,
                    name: "蝴蝶",
                    price: 8,
                    count: 5,
                    url: "http://www.jq22.com/img/cs/500x500-2.png"
                },
                {
                    id: 3,
                    name: "小狗",
                    price: 100,
                    count: 1,
                    url: "http://www.jq22.com/img/cs/500x500-3.png"
                },
                {
                    id: 4,
                    name: "鲜花",
                    price: 10,
                    count: 1,
                    url: "http://www.jq22.com/img/cs/500x500-4.png"
                }
            ],
            search: ""
        },
        methods: {

        },
        filters: { //过滤器
            numFilter: function(data, n) { //data==item.price 当前过滤的数据 n==2
                return "￥" + data.toFixed(n)
            }
        },
        computed: { //计算属性
            totalCount: function() {
                var n = 0;
                this.items.forEach((v, i) => {
                    n += v.count
                });
                return n;
            },
            totalPrice: function() {
                var money = 0;
                this.items.forEach((v, i) => {
                    money += v.count * v.price
                });
                return money;
            },
            searchFor: function() {
                if (!this.search) {
                    return this.items
                }
                return this.items.filter((v, i) => {
                    if (v.name.indexOf(this.search) !== -1) { //匹配成功
                        return v
                    }
                })
            }

        }
    })
}

//设置iframe高度
function setIframeHeight(sonH) { //debugger;            
    var height = 0;
    //比较父子页面高度，以高度更大的为准
    var parentH = $(window).height(); //iframe最小高度应为浏览器视口高度，否则门户管理页面弹窗大小会受限制
    height = parentH > sonH ? parentH : sonH;
    $('#mainIframe').height(height);

    //子页面有传值过来，覆盖iframe的最小高度-2000px
    $("#mainIframe").css("min-height", 'auto');
    $(".body-bg").css("height", height + 200);
    try {
        var childBody = $("#mainIframe")[0].contentWindow.document.getElementsByTagName("body")[0];
        //childBody.style.minHeight = height + "px";
    } catch (error) {
        if (error.message.indexOf("Blocked from frame") > -1) console.warn("当前页面存在跨域！");
    }
}


(function($) {
    $("#username").keyup(function(event) {
        if (event.keyCode == 13) $("#password").focus().select();
    });
    $("#password").keyup(function(event) {
        if (event.keyCode == 13) $("#login-button").click();
    });
})(jQuery);


//回到顶部
function goTop() {
    window.scrollTo({
        top: 0,
        behavior: 'smooth',
    });
}

window.onscroll = function() {
    var t = document.documentElement.scrollTop;
    if (t > 50) {
        $(".toTop").fadeIn();
    } else {
        $(".toTop").fadeOut();
    }
}


function urlAnalysis() {
    var url = window.location.href;
    var paraString = url.substring(url.indexOf("?") + 1, url.length);
    var indexFirst = paraString.indexOf("&");
    var paraStringTitle = paraString.slice(0, indexFirst);
    paraStringElse = paraString.slice(indexFirst + 1, paraString.length);
    var paraStringUrl = paraStringElse;

    //区分是否传参：functionId
    if (paraString.indexOf("functionId") > -1) {
        var indexSecond = paraStringElse.indexOf("&");
        var paraStringFId = paraStringElse.slice(0, indexSecond);

        var functionId = paraStringFId.split("=")[1];
        var $body = angular.element(document.body);
        var $rootScope = $body.scope().$root;
        $rootScope.navFunctionId = functionId;

        paraStringUrl = paraStringElse.slice(indexSecond + 1, paraStringElse.length);
    }

    var title = paraStringTitle.split("=")[1] === "undefined" ? "" : decodeURI(paraStringTitle.split("=")[1]);
    var indexUrl = paraStringUrl.indexOf("=");
    var iframeUrl = paraStringUrl.slice(indexUrl + 1, paraStringUrl.length);

    document.title = title;
    $("#mainIframe").attr("src", iframeUrl);
}



// 监听enter按下事件，页面跳转
$scope.enterEvent = function(e) {
    var keycode = window.event ? e.keyCode : e.which;
    if (keycode == 13) {
        console.log($scope.searchVal)
        console.log('监听成功')
        var baseUrl = '#/pages/knowlege/knowlegeSeach.html'
        window.open(baseUrl)
    }
};


function showDate() {
    var myDate = new Date();
    var year = myDate.getFullYear();
    var month = myDate.getMonth() + 1;
    month = month < 10 ? '0' + month : month;
    var date = myDate.getDate();
    date = date < 10 ? '0' + date : date;
    var weekDay = myDate.getDay();

    switch (weekDay) {
        case 0:
            weekDay = "天";
            break;
        case 1:
            weekDay = "一";
            break;
        case 2:
            weekDay = "二";
            break;
        case 3:
            weekDay = "三";
            break;
        case 4:
            weekDay = "四";
            break;
        case 5:
            weekDay = "五";
            break;
        case 6:
            weekDay = "六";
            break;
            "name"
    }

    $scope.year = year;
    $scope.month = month;
    $scope.date = date;
    $scope.weekDay = weekDay;
}


//获取跳转的classId,通过hash方式获取
$scope.getQueryString = function() {
    var obg = {},
        a = '';
    (a = window.location.search.substr(1)) || (a = window.location.hash.split('?')[1])
    a.split(/&/g).forEach(function(item) {
        obg[(item = item.split('='))[0]] = item[1];
    })
    return obg
}
var classId = $scope.getQueryString();

203.原生js滑块验证

//event.clientX:鼠标点下的点到左侧x轴的距离
window.onload = function() {
    //事件处理  onmousedown  onmousemove  onmouseup
    var box = document.querySelector(".box")
    var btn = document.querySelector(".btn")
    var bg = document.querySelector(".bg")
    var text1 = document.querySelector(".text")
    //封装的选择器 声明式函数可以提升
    //   function fun(){
    //    
    //   }
    var flag = false; //标记
    btn.onmousedown = function(event) {
        var downx = event.clientX; //按下后获取的与x轴的距离
        btn.onmousemove = function(e) {
            var movex = e.clientX - downx; //滑块滑动的距离
            //移动的范围
            if (movex > 0) {
                this.style.left = movex + "px";
                bg.style.width = movex + "px";
                if (movex >= box.offsetWidth - 40) {
                    //验证成功
                    flag = true
                    text1.innerHTML = "验证成功"
                    text1.style.color = "#fff"
                    //清除事件
                    btn.onmousedown = null;
                    btn.onmousemove = null;
                }
            }
        }
    }
    //松开事件
    btn.onmouseup = function() {
        //清除事件
        btn.onmousemove = null;
        if (flag) return;
        this.style.left = 0;
        bg.style.width = 0 + "px";
    }
}

204.纯 js无限加载瀑布（原创）

//随机[m,n]之间的整数 封装
function randomNumber(m, n) {
    return Math.floor(Math.random() * (n - m + 1) + m);
}
//随机颜色 封装
function randomColor() {
    return "rgb(" + randomNumber(0, 255) + "," + randomNumber(0, 255) + "," + randomNumber(0, 255) + ")";
}

//获取当前的scrollTop 
var scrollTopDistance;
//获取所有的ul 
var uls = document.querySelectorAll("ul");
var i = 0;
var k = i;

function waterFall() {
    for (i = k; i < k + 4; i++) {
        //创建li 
        var li = document.createElement("li");
        //随机颜色 
        li.style.backgroundColor = randomColor();
        //随机高度 
        li.style.height = randomNumber(120, 400) + "px";
        //手动转换为字符串 
        li.innerHTML = i + 1 + "";
        //插入到对应的ul中 
        //判断哪个ul的高度低，该次创建的li就插入到此ul中 
        var index = 0; //记录下标 
        for (var j = 0; j < uls.length; j++) {
            if (uls[j].offsetHeight < uls[index].offsetHeight) {
                index = j;
            }
        }
        //将元素节点插入文档中 
        uls[index].appendChild(li);
    }
    k = i;
    return uls[index].offsetHeight;
}
waterFall();
//鼠标滚轮事件,由于右侧没有滚轮，所以使用onmousewheel事件
window.onmousewheel = function() {
    //获取窗口的高度，要兼容浏览器
    var windowH = document.documentElement.clientHeight;
    //滚轮于top的距离，要兼容浏览器
    var scrollH = document.documentElement.scrollTop ||
        document.body.scrollTop;
    //获取窗口的可见高度
    var documentH = document.documentElement.scrollHeight ||
        document.body.scrollHeight;
    //窗口的高度 + 滚轮与顶部的距离 > 窗口的可见高度-200
    if (windowH + scrollH > documentH - 200) {
        //执行此函数 
        waterFall()
    }
}

205.jQuery两个元素比较高度

$(*function* () {
  *var* w_max = 0;
  *//求最大高度*
  $("#MenuNavigation li").each(*function* () {
​    *var* w = $(*this*).innerWidth();
​    w_max = w > w_max ? w : w_max;
  })
  $("#MenuNavigation li").width(w_max)
  *//将最大高度赋值给所有元素，*
})

206.js定时清除缓存，存储缓存，获取缓存

// 封装本地存储的方法
export const storage = {
  set: function(variable, value, ttl_ms) {
    var data = { value: value, expires_at: new Date(ttl_ms).getTime() };
    localStorage.setItem(variable.toString(), JSON.stringify(data));
  },
  get: function(variable) {
    var data = JSON.parse(localStorage.getItem(variable.toString()));
    if (data !== null) {
      debugger
      if (data.expires_at !== null && data.expires_at < new Date().getTime()) {
        localStorage.removeItem(variable.toString());
      } else {
        return data.value;
      }
    }
    return null;
  },
  remove(key) {
    localStorage.removeItem(key);
  }
}

207.数组降维

//数组降维
reduceDimension(arr) {
      var reduced = [];
      for (var i = 0; i < arr.length; i++) {
        reduced = reduced.concat(arr[i]);
      }
      return reduced;
}

208.设置cookie,获取cookie,删除cookie

var cookieUtil = {
  getCookie: function (name) {
    var arrCookie = document.cookie.split("; ");
    for (var i = 0; i < arrCookie.length; i++) {
      var cookieItem = arrCookie[i].split('=');
      if (cookieItem[0] == name) {
        return cookieItem[1];
      }
    }
    return undefined;
  },
  setCookie: function (name, value, expires, path, domain, secure) {
    var cookieText = encodeURIComponent(name) + "=" +
      encodeURIComponent(value);
    if (expires instanceof Date) {
      cookieText += "; expires=" + expires.toGMTString();
    }
    if (path) {
      cookieText += "; path=" + path;
    }
    if (domain) {
      cookieText += "; domain=" + domain;
    }
    if (secure) {
      cookieText += "; secure";
    }
    document.cookie = cookieText;
  },
  removeCookie: function (name, path, domain, secure) {
    this.set(name, "", new Date(0), path, domain, secure);
  }
} 

209.判读是否为外链

/**

 * @description 判读是否为外链
 * @param path
 * @returns {boolean}
   */
   export function isExternal(path) {
     return /^(https?:|mailto:|tel:)/.test(path);
   }

210.校验密码是否小于6位

/**
    * @description 校验密码是否小于6位
    * @param str
    * @returns {boolean}
      */
      export function isPassword(str) {
        return str.length >= 6;
      }