• js 的 document element 的 querySelectorAll写在for外内速度测试2207302107

    js 的 document element 的 querySelectorAll写在for外内速度测试2207302107

    使用变量,用时:42毫秒
    不使用变量,用时:67毫秒
    document.querySelectorAll().forEach( 用时:63毫秒
    执行document.querySelectorAll(“.SpanC1”) 500次,用时 973 毫秒

    点这里是用eval执行的版本,性能差别不大

    测试代码

    DOCTYPE html><html lang="zh-CN"><head><meta charset="utf-8"/><title>title><style>

body{margin:0}

#BodyH{display:flex; align-items:center; justify-content:flex-start; background-image:linear-gradient(to right, red, orange, yellow, green, cyan, blue, purple);}



style><script>
if(!document.title.length)(function(){var str=document.URL; str=str.substring( str.lastIndexOf("/")+1 , str.lastIndexOf('.')); str=decodeURI(str); document.title=str;})();

let isLog=true;clog=function(){if(isLog)for(let a of arguments)console.log(a);}; n09="0123456789"; lAZ="ABCDEFGHIJKLMNOPQRSTUVWXYZ"; laz="abcdefghijklmnopqrstuvwxyz"; Z62=n09+lAZ+laz; Z62o={};for(let i=0;i<Z62.length;i++)Z62o[Z62[i]]=i; const CTTT="Content-type";
rdmN=(u)=>parseInt(Math.random()*u); rdmV=(sa)=>sa[rdmN(sa.length)]; rdmS=(l=1,sample=Z62)=>{let s='';for(let i=0;i<l;i++)s+=rdmV(sample);return s;};
z62=z62l=(l)=>rdmS(l);		decFrZ62=(z)=>{let a=Array.from(z).reverse(); let i=0; for(let j=0;j<a.length;j++)i+=Z62o[a[j]]*Math.pow(62,j);return i;};
z62Now=()=>{let l=Date.now(),a=[]; while(l>62){a.push(Z62[l%62]);l=parseInt(l/62);};a.push(Z62[l]);return a.reverse().join('');};
z62Id=(l)=>{let s=z62Now(); if(l&&l>6){l-=6;s+=z62(l);}return s;};
rdmRgb=()=>'rgb('+rdmN(256)+','+rdmN(256)+','+rdmN(256)+')'; rdmBgc=()=>"background-color:"+rdmRgb()+";";

isA=(x)=>x&&x.constructor===Array,isS=(x)=>x&&x.constructor===String,isF=(x)=>x&&x.constructor===Function,isO=(x)=>x&&x.constructor===Object,isJ=(x)=>isA(x)||isO(x),isM=(x)=>x&&x.constructor===Map;
isE=(x,tn)=>{let b=(x&&x instanceof HTMLElement); if(b&&tn)b=(x.tagName===tn.toUpperCase()); return b;}; 
isColl=(x)=>x&&isFinite(x.length)&&x.constructor!==String;
isEnterEvent=(ev)=>ev&&(ev.which===13&&ev.keyCode===13&&ev.key==="Enter"&&ev.code==="Enter");
triggee=triggerElementEvent=触发元素的事件=(e,evn)=>{e=dgebi(e);e.dispatchEvent(new Event(evn)); return e;};
z24ParseInt=(s)=>{let ar=Array.from(s); let ar1=ar.filter((v)=>isFinite(v)); return parseInt(ar1.join(''));};
stringSeparator=(str,ss,hf)=>{if(!ss||ss.length===0)return str; let ar=str.split(ss.shift()); if(isF(hf))hf(ar); ar=ar.map((s)=>stringSeparator(s,ss.slice())); return ar;};
//ge //dgebi
const ge=window.dgebi=function(i,s){if(!i)return;let e=i;if(isS(i)){e=document.getElementById(i);if(!e)e=document.querySelector(i);} if(!s)return e; s=ge(s); if(isE(e)&&isE(s))e.appendChild(e.新娃=e.xw=s);else{clog("↓↓↓",e,"父或子不是Element",s,"↑↑↑");}return e;};
dce=window.dcept=(p,tn="DIV")=>{let e=document.createElement(tn);e.idefine=(i)=>{e.id=i;return window[i]=e;};e.htm=(h)=>{if(h!==undefined)e.innerHTML=h;return e;};
		e.ass=e.aCssText=(s)=>{if(s)e.style.cssText+=";"+s;return e;};e.cls=(c)=>{if(c!==undefined)e.className+=" "+c;return e;};
		e.ce=(a0,c2,h2)=>{let ar; if(isS(a0))ar=a0.split("=->");else ar=a0; let t=ar[0].replace(/\s/g,''),h=ar[1],ct=ar[2],c=ar[3]; e.ceLast=dcept(e,t).htm(h).htm(h2).aCssText(ct).cls(c).cls(c2); if(isS(ar[4]))eval("const P=e,I=e.ceLast;"+ar[4]); return e.ceLast};
		e.ca=(a0,c,h)=>{e.ce(a0,c,h);return e};
		e.cen=function(a0, n=1, c, f)	{e.cenAr=[];let ar;if(isS(a0))ar=a0.split('\n');else ar=a0; for(let t=0;t<n;t++)for(let tn of ar){let s=e.ce(tn).cls(c); if(f)f(s,e, e.cenAr); e.cenAr.push(s)};return e;};
		e.cbn=function(a0,n0=1,n1=1,c0,c1,f0,f1)	{let ar;if(isS(a0))ar=a0.split('\n');else ar=a0; let pt=ar.shift(); e.cen(pt,n0,c0,f0); for(let b of e.cenAr){b.cen(ar,n1,c1,f1);} return e;};
		e.rdmBgc=function(){e.style.backgroundColor=rdmRgb();return e;};
		dgebi(p,e);return e;};
window.dceptq=function(p,t,q=1){let ear=Array(q); for(let n=0;n<q;n++){ear.push(dcept(p,t));} return ear;};
dceptc=(p,t,c)=>dcept(p,t).cls(c); dcDiv=(p,c)=>dceptc(p,"div",c); dcArticle=(p,c)=>dceptc(p,"article",c); dcSection=(p,c)=>dceptc(p,"section",c);
dcFL=(p,lh,c)=>{let f=dcept(p,"fieldset").cls(c); f.l=dcept(f,"legend").htm(lh); return f;};
evalab=(p,code)=>dcept(p,"label").cls("evalab").cen("span=->"+code+"=->=->evalabL , span=->的结果是=->=->evalabC , span=->"+eval(code)+"=->=->evalabR");
window.dwbr=function(a0=1){let ar=arguments,br=dwbr.br; if(Number.isFinite(a0)){br(a0);return;} for(let a of ar)document.write(a.replace(/\n/g,"
    "    ));br();}; dwbr.br=function(n=1){for(let c=0;c<n;c++)document.write("
    "    );};
window.simpleTableByA2=(p,a2)=>{let tb=dcept(p,"table").cen(['thead','tbody','tfoot']);tb.h=tb.tHead;let tbd=tb.b=tb.tBody=tb.tBodies[0]; tb.f=tb.tFoot; tb.Ntr=dcept(tb.h,"tr","Ntr"); let ar=a2.shift(); ar.forEach((v)=>dce(tb.Ntr,"th").htm(v)); 
		a2.forEach((row,r)=>{let tr=dcept(tbd,"tr");row.forEach((v,c)=>{let td=dce(tr,"td").htm(v).cls("R"+r+"C"+c);});});return tb;};



    script>
head><body><header id="BodyH">

	<label>label><script>{let s=document.currentScript; let l=s.previousElementSibling; if(!l.innerHTML.length)l.textContent=document.title}script>

header><div id="BodyB">





div><script>const BodyH=dgebi("BodyH") , BodyB=dgebi("BodyB") ; dce(document.body).idefine("BodyF"); dce(BodyB).idefine("BBB");script>
<script>{

	
	let helloAr = dceptq(BBB,"hello",120);
	helloAr.forEach(v=>{
		v.cbn("world \n span=->spanTagC1=->=->SpanC1=->I.rdmBgc(); \n span=->spanTagC2=->=->SpanC2=->I.rdmBgc(); " , 20, 10);
	});
	
	{
		let beginning = Date.now();
		let es = document.querySelectorAll("hello");		for(let e of es){e.style.display="block";}
		es = document.querySelectorAll("world"); for(let e of es){e.style.display="block"; }
		es = document.querySelectorAll(".SpanC1");  es.forEach((e,i)=>{e.style.color="blue";});
		es = document.querySelectorAll(".spanC2"); es.forEach(e=>{e.style.color="gold";});

		let cost = Date.now()-beginning;
		let str = ("使用变量,用时:"+cost+"毫秒");
		dwbr(str);
		console.log(str);
	}
	{
		let beginning = Date.now();
		for(let e of document.querySelectorAll("hello")){e.style.display="block"; }
		for(let e of document.querySelectorAll("world")){e.style.display="block"; }
		for(let e of document.querySelectorAll(".SpanC1")){ e.style.color="blue"; }
		for(let e of document.querySelectorAll(".SpanC2")){ e.style.color="gold"; }

		let cost = Date.now()-beginning;
		let str = ("不使用变量,用时:"+cost+"毫秒");
		dwbr(str);
		console.log(str);
	}
	{
		let beginning = Date.now();
		document.querySelectorAll("hello").forEach(e=>e.style.display="block");
		document.querySelectorAll("world").forEach(e=>e.style.display="block");
		document.querySelectorAll(".SpanC1").forEach(e=>e.style.color="red"  );
		document.querySelectorAll(".SpanC2").forEach(e=>e.style.color="green" );
		
		let cost = Date.now()-beginning;
		let str = "document.querySelectorAll().forEach( 用时:"+cost+"毫秒";
		dwbr(str);
		console.log(str);
	}


	{
		let beginning = Date.now();
		let count = 500;

		for(let c=0;c<count;c++){
			let es = document.querySelectorAll(".SpanC1");
		}
		
		let cost = Date.now()-beginning;
		let str = '执行document.querySelectorAll(".SpanC1") '+count+"次,用时 "+cost+" 毫秒 ";
		dwbr(str);
		console.log(str);
	}










}script><style>
	*{box-sizing:border-box;}
	
	
	

style><script>{
	






}script><script>{


	






}script>body>html>







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    在这里插入图片描述

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  • 原文地址：https://blog.csdn.net/kfepiza/article/details/126106915