兼容

1. 兼容promise ：引入bluebird.js

2. 兼容媒体查询和layui栅格布局：引入html5shiv.js 和respond.js

3. 兼容console。ie8正式环境下console未定义，如果打包没有去掉console，会堵塞代码

   (function () {
    var method;
    var noop = function () { };
    var methods = [
        'assert', 'clear', 'count', 'debug', 'dir', 'dirxml', 'error',
        'exception', 'group', 'groupCollapsed', 'groupEnd', 'info', 'log',
        'markTimeline', 'profile', 'profileEnd', 'table', 'time', 'timeEnd',
        'timeline', 'timelineEnd', 'timeStamp', 'trace', 'warn'
    ];
    var length = methods.length;
    var console = (window.console = window.console || {});
   
    while (length--) {
        method = methods[length];
   
        // Only stub undefined methods.
        if (!console[method]) {
            console[method] = noop;
        }
    }
   }());

4. 判断ie版本

   function IEVersion() {
    var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串  
    var isIE = userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1; //判断是否IE<11浏览器  
    var isEdge = userAgent.indexOf("Edge") > -1 && !isIE; //判断是否IE的Edge浏览器  
    var isIE11 = userAgent.indexOf('Trident') > -1 && userAgent.indexOf("rv:11.0") > -1;
    if (isIE) {
        var reIE = new RegExp("MSIE (\\d+\\.\\d+);");
        reIE.test(userAgent);
        var fIEVersion = parseFloat(RegExp["$1"]);
        if (fIEVersion == 7) {
            return 7;
        } else if (fIEVersion == 8) {
            return 8;
        } else if (fIEVersion == 9) {
            return 9;
        } else if (fIEVersion == 10) {
            return 10;
        } else {
            return 6; //IE版本<=7
        }
    } else if (isEdge) {
        return 'edge'; //edge
    } else if (isIE11) {
        return 11; //IE11  
    } else {
        return -1; //不是ie浏览器
    }
   };

5. 兼容forEach

   ! function () {
    if (!Array.prototype.forEach) {
        Array.prototype.forEach = function (callback /*, thisArg*/) {
            var T, k;
            if (this == null) {
                throw new TypeError('this is null or not defined');
            }
            var O = Object(this);
            var len = O.length >>> 0;
            if (typeof callback !== 'function') {
                throw new TypeError(callback + ' is not a function');
            }
            if (arguments.length > 1) {
                T = arguments[1];
            }
            k = 0;
            while (k < len) {
                var kValue;
                if (k in O) {
                    kValue = O[k];
                    callback.call(T, kValue, k, O);
                }
                k++;
            }
        };
    }
   }();

6. 兼容indexOf()

   if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function (elt /*, from*/) {
        var len = this.length >>> 0;
        var from = Number(arguments[1]) || 0;
        from = (from < 0) ? Math.ceil(from) : Math.floor(from);
        if (from < 0)
            from += len;
        for (; from < len; from++) {
            if (from in this &&
                this[from] === elt)
                return from;
        }
        return -1;
    };
   }

7. 兼容opacity：filter: progid:DXImageTransform.Microsoft.Alpha(opacity=0.3)

8. 兼容圆角 引入PIE.htc

   x{
   -moz-border-radius: 15px;
   -webkit-border-radius: 15px;
   border-radius: 15px;
   behavior: url(./PIE.htc);//文件必须和html同级
   position: relative;
   }

问题

1. 数组结尾不能有逗号，ie8中循环会生成一项empty

下载

• ie8只能让后端返回文件地址，window.open(地址)，a标签，window.location.href='地址'，下载
• ie10及以上；后端返回文件流，可以使用blob下载

有的问题没有记录，像es6,html5的部分东西直接不用就行