跪求！js 函数报错如下？怎么回事哈啊？

Question

functionunique(arr){returnarr.reduce((prev,cur)=>prev.includes(cur)?prev:[...prev,cur],[]);}vararr=[1,1,'true','true',true,true,15,15,false,false,undefined,undefined,null,null,NaN,NaN,'NaN',0,0,'a','a',{},{}];console.log(unique(arr));//正常打印functionunique(arr){returnarr.reduce((prev,cur)=>{returnprev.includes(cur)?prev:[...prev,cur],[];});}vararr=[1,1,'true','true',true,true,15,15,false,false,undefined,undefined,null,null,NaN,NaN,'NaN',0,0,'a','a',{},{}];console.log(unique(arr));//错报问题描述更改了箭头函数的写法为什么就会报错？UncaughtTypeError:prev.includesisnotafunction

Answer 1

reduce的第二个参数没传functionunique(arr){returnarr.reduce((prev,cur)=>{returnprev.includes(cur)?prev:[...prev,cur];},[]);}vararr=[1,1,'true','true',true,true,15,15,false,false,undefined,undefined,null,null,NaN,NaN,'NaN',0,0,'a','a',{},{}];console.log(unique(arr));

Answer 2

functionunique(arr){returnarr.reduce((prev,cur)=>{returnprev.includes(cur)?prev:[...prev,cur];},[]);}vararr=[1,1,'true','true',true,true,15,15,false,false,undefined,undefined,null,null,NaN,NaN,'NaN',0,0,'a','a',{},{}];console.log(unique(arr));