کار js زیر چیست
(function(){var t,e,n,r,s,o,i,a,u,c,l,p,h,f,d,g,m,y,v,w,b,k,S,q,L,x,T,R,P,E,M,j,A,N,O,_,F,C,U,W,X,D,H,I,z,G,B,J,K=[].slice,Q={}.hasOwnProperty,V=function(t,e){function n(){this.constructor=t}for(var r in e)Q.call(e,r)&&(t[r]=e[r]);return n.prototype=e.prototype,t.prototype=new n,t.__super__=e.prototype,t},Y=[].indexOf||function(t){for(var e=0,n=this.length;n>e;e++)if(e in this&&this[e]===t)return e;return-1};for(b={catchupTime:100,initialRate:.03,minTime:250,ghostTime:100,maxProgressPerFrame:20,easeFactor:1.25,startOnPageLoad:!0,restartOnPushState:!0,restartOnRequestAfter:500,target:"body",elements:{checkInterval:100,selectors:["body"]},eventLag:{minSamples:10,sampleCount:3,lagThreshold:3},ajax:{trackMethods:["GET"],trackWebSockets:!0,ignoreURLs:[]}},P=function(){var t;return null!=(t="undefined"!=typeof performance&&null!==performance&&"function"==typeof performance.now?performance.now():void 0)?t:+new Date},M=window.requestAnimationFrame||window.mozRequestAnimationFrame||window.webkitRequestAnimationFrame||window.msRequestAnimationFrame,w=window.cancelAnimationFrame||window.mozCancelAnimationFrame,null==M&&(M=function(t){return setTimeout(t,50)},w=function(t){return clearTimeout(t)}),A=function(t){var e,n;return e=P(),(n=function(){var r;return(r=P()-e)>=33?(e=P(),t(r,function(){return M(n)})):setTimeout(n,33-r)})()},j=function(){var t,e,n;return n=arguments[0],e=arguments[1],t=3<=arguments.length?K.call(arguments,2):[],"function"==typeof n[e]?n[e].apply(n,t):n[e]},k=function(){var t,e,n,r,s,o,i;for(e=arguments[0],o=0,i=(r=2<=arguments.length?K.call(arguments,1):[]).length;i>o;o++)if(n=r[o])for(t in n)Q.call(n,t)&&(s=n[t],null!=e[t]&&"object"==typeof e[t]&&null!=s&&"object"==typeof s?k(e[t],s):e[t]=s);return e},m=function(t){var e,n,r,s,o;for(n=e=0,s=0,o=t.length;o>s;s++)r=t[s],n+=Math.abs(r),e++;return n/e},q=function(t,e){var n,r,s;if(null==t&&(t="options"),null==e&&(e=!0),s=document.querySelector("[data-pace-"+t+"]")){if(n=s.getAttribute("data-pace-"+t),!e)return n;try{return JSON.parse(n)}catch(t){return r=t,"undefined"!=typeof console&&null!==console?console.error("Error parsing inline pace options",r):void 0}}},i=function(){function t(){}return t.prototype.on=function(t,e,n,r){var s;return null==r&&(r=!1),null==this.bindings&&(this.bindings={}),null==(s=this.bindings)[t]&&(s[t]=[]),this.bindings[t].push({handler:e,ctx:n,once:r})},t.prototype.once=function(t,e,n){return this.on(t,e,n,!0)},t.prototype.off=function(t,e){var n,r,s;if(null!=(null!=(r=this.bindings)?r[t]:void 0)){if(null==e)return delete this.bindings[t];for(n=0,s=[];n<this.bindings[t].length;)s.push(this.bindings[t][n].handler===e?this.bindings[t].splice(n,1):n++);return s}},t.prototype.trigger=function(){var t,e,n,r,s,o,i,a,u;if(n=arguments[0],t=2<=arguments.length?K.call(arguments,1):[],null!=(i=this.bindings)?i[n]:void 0){for(s=0,u=[];s<this.bindings[n].length;)r=(a=this.bindings[n][s]).handler,e=a.ctx,o=a.once,r.apply(null!=e?e:this,t),u.push(o?this.bindings[n].splice(s,1):s++);return u}},t}(),c=window.Pace||{},window.Pace=c,k(c,i.prototype),E=c.options=k({},b,window.paceOptions,q()),H=0,z=(B=["ajax","document","eventLag","elements"]).length;z>H;H++)!0===E[F=B[H]]&&(E[F]=b[F]);u=function(t){function e(){return e.__super__.constructor.apply(this,arguments)}return V(e,t),e}(Error),e=function(){function t(){this.progress=0}return t.prototype.getElement=function(){var t;if(null==this.el){if(!(t=document.querySelector(E.target)))throw new u;this.el=document.createElement("div"),this.el.className="pace pace-active",document.body.className=document.body.className.replace(/pace-done/g,""),document.body.className+=" pace-running",this.el.innerHTML='<div class="pace-progress">\n  <div class="pace-progress-inner"></div>\n</div>\n<div class="pace-activity"></div>',null!=t.firstChild?t.insertBefore(this.el,t.firstChild):t.appendChild(this.el)}return this.el},t.prototype.finish=function(){var t;return(t=this.getElement()).className=t.className.replace("pace-active",""),t.className+=" pace-inactive",document.body.className=document.body.className.replace("pace-running",""),document.body.className+=" pace-done"},t.prototype.update=function(t){return this.progress=t,this.render()},t.prototype.destroy=function(){try{this.getElement().parentNode.removeChild(this.getElement())}catch(t){u=t}return this.el=void 0},t.prototype.render=function(){var t,e,n,r,s,o,i;if(null==document.querySelector(E.target))return!1;for(t=this.getElement(),r="translate3d("+this.progress+"%, 0, 0)",s=0,o=(i=["webkitTransform","msTransform","transform"]).length;o>s;s++)e=i[s],t.children[0].style[e]=r;return(!this.lastRenderedProgress||this.lastRenderedProgress|0!==this.progress|0)&&(t.children[0].setAttribute("data-progress-text",(0|this.progress)+"%"),this.progress>=100?n="99":(n=this.progress<10?"0":"",n+=0|this.progress),t.children[0].setAttribute("data-progress",""+n)),this.lastRenderedProgress=this.progress},t.prototype.done=function(){return this.progress>=100},t}(),a=function(){function t(){this.bindings={}}return t.prototype.trigger=function(t,e){var n,r,s,o,i;if(null!=this.bindings[t]){for(i=[],r=0,s=(o=this.bindings[t]).length;s>r;r++)n=o[r],i.push(n.call(this,e));return i}},t.prototype.on=function(t,e){var n;return null==(n=this.bindings)[t]&&(n[t]=[]),this.bindings[t].push(e)},t}(),D=window.XMLHttpRequest,X=window.XDomainRequest,W=window.WebSocket,S=function(t,e){var n,r,s;for(n in s=[],e.prototype)try{r=e.prototype[n],s.push(null==t[n]&&"function"!=typeof r?t[n]=r:void 0)}catch(t){t}return s},T=[],c.ignore=function(){var t,e,n;return e=arguments[0],t=2<=arguments.length?K.call(arguments,1):[],T.unshift("ignore"),n=e.apply(null,t),T.shift(),n},c.track=function(){var t,e,n;return e=arguments[0],t=2<=arguments.length?K.call(arguments,1):[],T.unshift("track"),n=e.apply(null,t),T.shift(),n},_=function(t){var e;if(null==t&&(t="GET"),"track"===T[0])return"force";if(!T.length&&E.ajax){if("socket"===t&&E.ajax.trackWebSockets)return!0;if(e=t.toUpperCase(),Y.call(E.ajax.trackMethods,e)>=0)return!0}return!1},l=function(t){function e(){var t,n=this;e.__super__.constructor.apply(this,arguments),t=function(t){var e;return e=t.open,t.open=function(r,s){return _(r)&&n.trigger("request",{type:r,url:s,request:t}),e.apply(t,arguments)}},window.XMLHttpRequest=function(e){var n;return n=new D(e),t(n),n};try{S(window.XMLHttpRequest,D)}catch(t){}if(null!=X){window.XDomainRequest=function(){var e;return e=new X,t(e),e};try{S(window.XDomainRequest,X)}catch(t){}}if(null!=W&&E.ajax.trackWebSockets){window.WebSocket=function(t,e){var r;return r=null!=e?new W(t,e):new W(t),_("socket")&&n.trigger("request",{type:"socket",url:t,protocols:e,request:r}),r};try{S(window.WebSocket,W)}catch(t){}}}return V(e,a),e}(),I=null,O=function(t){var e,n,r,s;for(n=0,r=(s=E.ajax.ignoreURLs).length;r>n;n++)if("string"==typeof(e=s[n])){if(-1!==t.indexOf(e))return!0}else if(e.test(t))return!0;return!1},(L=function(){return null==I&&(I=new l),I})().on("request",function(e){var n,r,s,o,i;return o=e.type,s=e.request,i=e.url,O(i)?void 0:c.running||!1===E.restartOnRequestAfter&&"force"!==_(o)?void 0:(r=arguments,"boolean"==typeof(n=E.restartOnRequestAfter||0)&&(n=0),setTimeout(function(){var e,n,i,a,u;if("socket"===o?s.readyState<2:0<(i=s.readyState)&&4>i){for(c.restart(),u=[],e=0,n=(a=c.sources).length;n>e;e++){if((F=a[e])instanceof t){F.watch.apply(F,r);break}u.push(void 0)}return u}},n))}),t=function(){function t(){var t=this;this.elements=[],L().on("request",function(){return t.watch.apply(t,arguments)})}return t.prototype.watch=function(t){var e,n,r,s;return r=t.type,e=t.request,s=t.url,O(s)?void 0:(n="socket"===r?new f(e):new d(e),this.elements.push(n))},t}(),d=function(){return function(t){var e,n,r,s,o,i=this;if(this.progress=0,null!=window.ProgressEvent)for(t.addEventListener("progress",function(t){return i.progress=t.lengthComputable?100*t.loaded/t.total:i.progress+(100-i.progress)/2},!1),n=0,r=(o=["load","abort","timeout","error"]).length;r>n;n++)e=o[n],t.addEventListener(e,function(){return i.progress=100},!1);else s=t.onreadystatechange,t.onreadystatechange=function(){var e;return 0===(e=t.readyState)||4===e?i.progress=100:3===t.readyState&&(i.progress=50),"function"==typeof s?s.apply(null,arguments):void 0}}}(),f=function(){return function(t){var e,n,r,s,o=this;for(this.progress=0,n=0,r=(s=["error","open"]).length;r>n;n++)e=s[n],t.addEventListener(e,function(){return o.progress=100},!1)}}(),r=function(){return function(t){var e,n,r,o;for(null==t&&(t={}),this.elements=[],null==t.selectors&&(t.selectors=[]),n=0,r=(o=t.selectors).length;r>n;n++)e=o[n],this.elements.push(new s(e))}}(),s=function(){function t(t){this.selector=t,this.progress=0,this.check()}return t.prototype.check=function(){var t=this;return document.querySelector(this.selector)?this.done():setTimeout(function(){return t.check()},E.elements.checkInterval)},t.prototype.done=function(){return this.progress=100},t}(),n=function(){function t(){var t,e,n=this;this.progress=null!=(e=this.states[document.readyState])?e:100,t=document.onreadystatechange,document.onreadystatechange=function(){return null!=n.states[document.readyState]&&(n.progress=n.states[document.readyState]),"function"==typeof t?t.apply(null,arguments):void 0}}return t.prototype.states={loading:0,interactive:50,complete:100},t}(),o=function(){return function(){var t,e,n,r,s,o=this;this.progress=0,t=0,s=[],r=0,n=P(),e=setInterval(function(){var i;return i=P()-n-50,n=P(),s.push(i),s.length>E.eventLag.sampleCount&&s.shift(),t=m(s),++r>=E.eventLag.minSamples&&t<E.eventLag.lagThreshold?(o.progress=100,clearInterval(e)):o.progress=3/(t+3)*100},50)}}(),h=function(){function t(t){this.source=t,this.last=this.sinceLastUpdate=0,this.rate=E.initialRate,this.catchup=0,this.progress=this.lastProgress=0,null!=this.source&&(this.progress=j(this.source,"progress"))}return t.prototype.tick=function(t,e){var n;return null==e&&(e=j(this.source,"progress")),e>=100&&(this.done=!0),e===this.last?this.sinceLastUpdate+=t:(this.sinceLastUpdate&&(this.rate=(e-this.last)/this.sinceLastUpdate),this.catchup=(e-this.progress)/E.catchupTime,this.sinceLastUpdate=0,this.last=e),e>this.progress&&(this.progress+=this.catchup*t),n=1-Math.pow(this.progress/100,E.easeFactor),this.progress+=n*this.rate*t,this.progress=Math.min(this.lastProgress+E.maxProgressPerFrame,this.progress),this.progress=Math.max(0,this.progress),this.progress=Math.min(100,this.progress),this.lastProgress=this.progress,this.progress},t}(),C=null,N=null,y=null,U=null,g=null,v=null,c.running=!1,x=function(){return E.restartOnPushState?c.restart():void 0},null!=window.history.pushState&&(G=window.history.pushState,window.history.pushState=function(){return x(),G.apply(window.history,arguments)}),null!=window.history.replaceState&&(J=window.history.replaceState,window.history.replaceState=function(){return x(),J.apply(window.history,arguments)}),p={ajax:t,elements:r,document:n,eventLag:o},(R=function(){var t,n,r,s,o,i,a,u;for(c.sources=C=[],n=0,s=(i=["ajax","elements","document","eventLag"]).length;s>n;n++)!1!==E[t=i[n]]&&C.push(new p[t](E[t]));for(r=0,o=(u=null!=(a=E.extraSources)?a:[]).length;o>r;r++)F=u[r],C.push(new F(E));return c.bar=y=new e,N=[],U=new h})(),c.stop=function(){return c.trigger("stop"),c.running=!1,y.destroy(),v=!0,null!=g&&("function"==typeof w&&w(g),g=null),R()},c.restart=function(){return c.trigger("restart"),c.stop(),c.start()},c.go=function(){var t;return c.running=!0,y.render(),t=P(),v=!1,g=A(function(e,n){var r,s,o,i,a,u,l,p,f,d,g,m,w,b,k;for(100-y.progress,s=d=0,o=!0,u=g=0,w=C.length;w>g;u=++g)for(F=C[u],f=null!=N[u]?N[u]:N[u]=[],l=m=0,b=(a=null!=(k=F.elements)?k:[F]).length;b>m;l=++m)i=a[l],o&=(p=null!=f[l]?f[l]:f[l]=new h(i)).done,p.done||(s++,d+=p.tick(e));return r=d/s,y.update(U.tick(e,r)),y.done()||o||v?(y.update(100),c.trigger("done"),setTimeout(function(){return y.finish(),c.running=!1,c.trigger("hide")},Math.max(E.ghostTime,Math.max(E.minTime-(P()-t),0)))):n()})},c.start=function(t){k(E,t),c.running=!0;try{y.render()}catch(t){u=t}return document.querySelector(".pace")?(c.trigger("start"),c.go()):setTimeout(c.start,50)},"function"==typeof define&&define.amd?define(function(){return c}):"object"==typeof exports?module.exports=c:E.startOnPageLoad&&c.start()}).call(this);