为什么这段函数运行的不符合预期？

Question

var a = ["a","b","c"];var b = ["a","b"];function diff(arr1,arr2){     var newArr = arr1.length>=arr2.length?arr1:arr2.filter(function(ele){        if(arr1.length>=arr2.length?arr2:arr1.indexOf(ele)==-1){          return ele       }     })           return newArr;  }diff(a,b)结果是["a", "b", "c"]而a.filter(function(ele){      if(b.indexOf(ele)==-1){           return ele       } })的结果是["c"]在函数中arr1.length>=arr2.length?arr1:arr2结果确实是数组a。arr1.length>=arr2.length?arr2:arr1也确实是数组b但运行结果却是不一样。这是为什么？

Answer 1

因为.运算符的优先级高于:运算符啊,
var newArr = arr1.length>=arr2.length?arr1:arr2.filter实际上是
var newArr = arr1.length>=arr2.length?arr1:(arr2.filter)
你要的是(var newArr = （arr1.length>=arr2.length?arr1:arr2）.filter)
看懂了吗？