jsPDF和html2canvas兼容IE11

之前写了利用jsPDF和html2canvas做多页PDF导出，但是发现在IE下面不行，存在BUG，也就是Promise未定义的问题，于是也一起处理了一下。
起先我想打算用bluebird.js，但是发现与现有项目代码存在冲突，所以先放弃了，然后采用了第二种方式通过引用polyfill.js可以解决这个问题：

polyfill.js：

(function(t){"use strict";if(!t.matches&&t.matchesSelector){t.matches=t.matchesSelector}if(!t.matches&&!t.matchesSelector){t.matches=function(t){var e=document.querySelectorAll(t),n=this;return Array.prototype.some.call(e,function(t){return t===n})}}})(Element.prototype);(function(t){"use strict";if(typeof t.Promise==="undefined"||t.Promise.toString().indexOf("[native code]")===-1){var e="[[PromiseStatus]]";var n="[[PromiseValue]]";var r="pending";var i="internal pending";var o="resolved";var s="rejected";var c=function(t,s){if(t[e]===i){t=t[n]}if(t[e]===r){t.deferreds.push(s)}else{t.handled=true;setTimeout(function(){var r=t[e]===o?s.onFulfilled:s.onRejected;if(r){try{a(s.promise,r(t[n]))}catch(t){u(s.promise,t)}}else{if(t[e]===o){a(s.promise,t[n])}else{u(s.promise,t[n])}}},0)}};var a=function(t,r){if(r===t){throw new TypeError("A promise cannot be resolved with it promise.")}try{if(r&&(typeof r==="object"||typeof r==="function")){if(r instanceof p){t[e]=i;t[n]=r;f(t);return}else 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e.element!=t});if(!this._observationTargets.length){this._unmonitorIntersections();this._unregisterInstance()}};i.prototype.disconnect=function(){this._observationTargets=[];this._unmonitorIntersections();this._unregisterInstance()};i.prototype.takeRecords=function(){var t=this._queuedEntries.slice();this._queuedEntries=[];return t};i.prototype._initThresholds=function(t){var e=t||[0];if(!Array.isArray(e))e=[e];return e.sort().filter(function(t,e,n){if(typeof t!="number"||isNaN(t)||t<0||t>1){throw new Error("threshold must be a number between 0 and 1 inclusively")}return t!==n[e-1]})};i.prototype._parseRootMargin=function(t){var e=t||"0px";var n=e.split(/\s+/).map(function(t){var e=/^(-?\d*\.?\d+)(px|%)$/.exec(t);if(!e){throw new Error("rootMargin must be specified in pixels or percent")}return{value:parseFloat(e[1]),unit:e[2]}});n[1]=n[1]||n[0];n[2]=n[2]||n[0];n[3]=n[3]||n[1];return n};i.prototype._monitorIntersections=function(){if(!this._monitoringIntersections){this._monitoringIntersections=true;if(this.POLL_INTERVAL){this._monitoringInterval=setInterval(this._checkForIntersections,this.POLL_INTERVAL)}else{c(t,"resize",this._checkForIntersections,true);c(e,"scroll",this._checkForIntersections,true);if(this.USE_MUTATION_OBSERVER&&"MutationObserver"in t){this._domObserver=new MutationObserver(this._checkForIntersections);this._domObserver.observe(e,{attributes:true,childList:true,characterData:true,subtree:true})}}}};i.prototype._unmonitorIntersections=function(){if(this._monitoringIntersections){this._monitoringIntersections=false;clearInterval(this._monitoringInterval);this._monitoringInterval=null;a(t,"resize",this._checkForIntersections,true);a(e,"scroll",this._checkForIntersections,true);if(this._domObserver){this._domObserver.disconnect();this._domObserver=null}}};i.prototype._checkForIntersections=function(){var t=this._rootIsInDom();var e=t?this._getRootRect():h();this._observationTargets.forEach(function(n){var i=n.element;var s=f(i);var c=this._rootContainsTarget(i);var a=n.entry;var u=t&&c&&this._computeTargetAndRootIntersection(i,e);var h=n.entry=new r({time:o(),target:i,boundingClientRect:s,rootBounds:e,intersectionRect:u});if(!a){this._queuedEntries.push(h)}else if(t&&c){if(this._hasCrossedThreshold(a,h)){this._queuedEntries.push(h)}}else{if(a&&a.isIntersecting){this._queuedEntries.push(h)}}},this);if(this._queuedEntries.length){this._callback(this.takeRecords(),this)}};i.prototype._computeTargetAndRootIntersection=function(n,r){if(t.getComputedStyle(n).display=="none")return;var i=f(n);var o=i;var s=p(n);var c=false;while(!c){var a=null;var h=s.nodeType==1?t.getComputedStyle(s):{};if(h.display=="none")return;if(s==this.root||s==e){c=true;a=r}else{if(s!=e.body&&s!=e.documentElement&&h.overflow!="visible"){a=f(s)}}if(a){o=u(a,o);if(!o)break}s=p(s)}return o};i.prototype._getRootRect=function(){var t;if(this.root){t=f(this.root)}else{var n=e.documentElement;var r=e.body;t={top:0,left:0,right:n.clientWidth||r.clientWidth,width:n.clientWidth||r.clientWidth,bottom:n.clientHeight||r.clientHeight,height:n.clientHeight||r.clientHeight}}return this._expandRectByRootMargin(t)};i.prototype._expandRectByRootMargin=function(t){var e=this._rootMarginValues.map(function(e,n){return e.unit=="px"?e.value:e.value*(n%2?t.width:t.height)/100});var n={top:t.top-e[0],right:t.right+e[1],bottom:t.bottom+e[2],left:t.left-e[3]};n.width=n.right-n.left;n.height=n.bottom-n.top;return n};i.prototype._hasCrossedThreshold=function(t,e){var n=t&&t.isIntersecting?t.intersectionRatio||0:-1;var r=e.isIntersecting?e.intersectionRatio||0:-1;if(n===r)return;for(var i=0;i<this.thresholds.length;i++){var o=this.thresholds[i];if(o==n||o==r||o<n!==o<r){return true}}};i.prototype._rootIsInDom=function(){return!this.root||l(e,this.root)};i.prototype._rootContainsTarget=function(t){return l(this.root||e,t)};i.prototype._registerInstance=function(){if(n.indexOf(this)<0){n.push(this)}};i.prototype._unregisterInstance=function(){var t=n.indexOf(this);if(t!=-1)n.splice(t,1)};function o(){return t.performance&&performance.now&&performance.now()}function s(t,e){var n=null;return function(){if(!n){n=setTimeout(function(){t();n=null},e)}}}function c(t,e,n,r){if(typeof t.addEventListener=="function"){t.addEventListener(e,n,r||false)}else if(typeof t.attachEvent=="function"){t.attachEvent("on"+e,n)}}function a(t,e,n,r){if(typeof t.removeEventListener=="function"){t.removeEventListener(e,n,r||false)}else if(typeof t.detatchEvent=="function"){t.detatchEvent("on"+e,n)}}function u(t,e){var n=Math.max(t.top,e.top);var r=Math.min(t.bottom,e.bottom);var i=Math.max(t.left,e.left);var o=Math.min(t.right,e.right);var s=o-i;var c=r-n;return s>=0&&c>=0&&{top:n,bottom:r,left:i,right:o,width:s,height:c}}function f(t){var e;try{e=t.getBoundingClientRect()}catch(t){}if(!e)return 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bluebird.js：
bluebird.js代码量比较大，我就不贴出来了，需要的小伙伴可以去搜索一下，应该马上就能找到的，IE的坑虽然有点小多，但是慢慢填也就填完了，加油