https://www.also.pt/js/webtrekk/4.5.8/webtrekk_page_load_time.js?v=buildNumber

1
2var wt_pageLoadTime=function(conf){
3	if(conf.mode=="page"&&conf.type=="before"&&conf.requestCounter==1){
4		this.pageLoadTime={
5			"samplingRate" : 0
6		};
7		this.sendPageLoadTime=function(){var wt_lt=wt_plt.performance.timing.loadEventStart-wt_plt.performance.timing.fetchStart;if(wt_lt&&wt_lt!==null&&wt_lt>0){if(!wt_plt.customParameter){wt_plt.customParameter={};};wt_plt.customParameter[570]=""+wt_lt;};if(typeof(wt_plt.campaignIdSwitch)!=="undefined"){wt_plt.campaignId=wt_plt.campaignIdSwitch;}wt_plt.sendinfo(false,false,"heatmap",false);wt_plt.campaignId=false;};this.performance=false;if(typeof(window.performance)!=="undefined"){this.performance=window.performance;}else if(typeof(window.webkitPerformance)!=="undefined"){this.performance=window.webkitPerformance;};if(this.performance&&typeof(this.performance.timing)!=="undefined"){var samplingRate=((this.pageLoadTime.samplingRate)?this.pageLoadTime.samplingRate:3);if(Math&&Math.random&&parseInt(Math.random()*parseInt(samplingRate))==0){if(!this.deactivatePixel&&!this.orderId){this.deactivateRequest=true;window.wt_plt=this;if(this.config.campaignId){this.campaignIdSwitch=this.config.campaignId;this.config.campaignId=false;}if(document.readyState=="complete"){wt_plt.sendPageLoadTime();}else{this.registerEvent(window,"load",wt_plt.sendPageLoadTime);}}}}
8	}
9};