1、2018/1/7Item 1:for 循環(huán)性能優(yōu)化有兩個(gè)因素決定循環(huán)展開是否有利執(zhí)行時(shí)間減少：1. 循環(huán)迭代的次數(shù)，成千上百次迭代才能帶來明顯的區(qū)別2. 循環(huán)體開銷/循環(huán)開銷比例=系數(shù)，系數(shù)越大，代表性能提升越少。循環(huán)展開：for(var i=0;i<8;i+)/do someth ing為了提升效率：將它展開為循環(huán)體8次。Item 2:JQuery代碼性能優(yōu)化一個(gè)JQuery代碼$( “#element ”).css(, color ? ,? #f00 ?);執(zhí)行過程調(diào)用JQuery并在DOM 搜索id= “element1 "的元素，正則測(cè)試返回搜索到的元素列表調(diào)用JQue

2、ry的css ()函數(shù)。這個(gè)可以進(jìn)行2點(diǎn)優(yōu)化：1. 指定JQuery搜索的范圍-環(huán)境參數(shù)選擇/$alien=$('.alien ' container)環(huán)境參數(shù) container可以是一個(gè) JQuery 對(duì)象或者 CSS 選擇器$alien(' .alien ' ,$container); /JQuery 對(duì)象$alien('.alien ' ,' #container ' ); /CSS 選擇器2. 保存對(duì)象引用var elementStyle=$( element1 'O.style;elementStyle.col

3、or=''保存對(duì)象引用，會(huì)減少搜索次數(shù)，從而優(yōu)化執(zhí)行性能。Item 3 : optimize DOM insertionYour APP may n eed large amou nt of DOM operati on ,DOM is a complicated datastructure that you should better not to modify it. But it is not that really for dynamicweb pages,so you should insert the elements in more effiective way.For example,you want to insert a ' <p>content</p>'.But whe n you want to in sert hun dreds of eleme nts,you should assembly it intoa long String,and insert it at once.This will dramatically decrese the overhead of JQuery in teral test and fun cti on$ ( ' #element1 &