题解 | #Array.reduce#
Array.reduce
https://www.nowcoder.com/practice/213d0ef21cb841de8cf69fcc5ea60eb6
Array.prototype._reduce = function(fn, sum=0) {
if(typeof fn !== 'function') return
for(let i=0;i<this.length;i++){
sum=fn(sum,this[i])
}
return sum
}
