面試時(shí)經(jīng)常被問到數(shù)組去重的問題，個(gè)人覺得這種問題其實(shí)沒太大的作用，畢竟在實(shí)際工作中很少能遇到的很大的數(shù)組，所以不論以什么樣的方式實(shí)現(xiàn)都很難做到內(nèi)存的溢出及產(chǎn)生較大的耗時(shí)差距(除非你是故意)?????????????? 今天咱們對(duì)比一下那個(gè)速度更快
function createTestArray(){
const testArray=[1,2,3,4,5,'a','b','c','d','e'];
for(let i=0;i<13;i++){
testArray.push(...testArray);
}
testArray.sort((a,b)=>Math.random()>0.5?1:-1);
//console.log(`testArray:${testArray},length:${testArray.length}`);
return testArray;
}
const testArray=createTestArray();
function showTime(fun){
const start=new Date();
const result=fun();
return `name:${fun.name},time:${new Date()-start},result:${result.join(',')}`;
}
function removeRepeatBySet(){
return [...new Set(testArray)];
}
function removeRepeatByFilter(){
return testArray.filter((item,index,arr)=>arr.indexOf(item)==index);
}
function removeRepeatByForof(){
const obj={},arr=[],value={};
for(let i of testArray){
if(obj[i]==value){
continue;
}else if(obj[i]!=value){
obj[i]=value;
arr.push(i);
}
}
return arr;
}
function removeRepeatByFor(){
const obj={},arr=[],value={};
for(let i= 0,len=testArray.length;i
const item=testArray[i];
if(obj[item]==value){
continue;
}else if(obj[item]!=value){
obj[item]=value;
arr.push(item);
}
}
return arr;
}
const results=[];
for(var i=0;i<10;i++){
results.push(
showTime(removeRepeatBySet),
showTime(removeRepeatByForof),
showTime(removeRepeatByFilter),
showTime(removeRepeatByFor)
);
}
console.log(JSON.stringify(results.sort(),null,4));
打印的結(jié)果
[
"name:removeRepeatByFilter,time:10,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:10,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:12,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:6,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:7,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:7,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:8,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFilter,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:2,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:3,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:3,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:3,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:3,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:4,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:4,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:4,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:5,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByFor,time:6,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:11,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:6,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:6,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:7,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:8,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:8,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:8,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatByForof,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:10,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:13,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:16,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:6,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:7,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:7,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:8,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:9,result:3,5,a,b,1,4,c,2,e,d",
"name:removeRepeatBySet,time:9,result:3,5,a,b,1,4,c,2,e,d"
]
此時(shí)我們可以看出。? for循環(huán)是用時(shí)最少的，其次for of，filter，而es6的Set用時(shí)最長(zhǎng)
