js performance.timing：利用performance.timing进行性能分析

window.onload = function(){setTimeout(function(){let t = performance.timingconsole.log('DNS查询耗时 ：' + (t.domainLookupEnd - t.domainLookupStart).toFixed(0))console.log('TCP链接耗时 ：' + (t.connectEnd - t.connectStart).toFixed(0))console.log('request请求耗时 ：' + (t.responseEnd - t.responseStart).toFixed(0))console.log('解析dom树耗时 ：' + (t.domComplete - t.domInteractive).toFixed(0))console.log('白屏时间 ：' + (t.responseStart - t.navigationStart).toFixed(0))console.log('domready时间 ：' + (t.domContentLoadedEventEnd - t.navigationStart).toFixed(0))console.log('onload时间 ：' + (t.loadEventEnd - t.navigationStart).toFixed(0))if(t = performance.memory){console.log('js内存使用占比 ：' + (t.usedJSHeapSize / t.totalJSHeapSize * 100).toFixed(2) + '%')}})}