题解 | #Array.reduce#
Array.reduce
https://www.nowcoder.com/practice/213d0ef21cb841de8cf69fcc5ea60eb6
Array.prototype._reduce = function(fn, prev){
if(typeof fn !== 'function') return;
for(let i = 0; i < this.length; i++){
if(prev == undefined){
prev = fn(this[i], this[i+1]);
i++;
}
else{
prev = fn(prev, this[i])
}
}
return prev;
}
