Faster alternative for Array.reduce()

aggregate.js

Array.prototype.aggregate = function (fn, initialValue) {
    let current
    const length = this.length
    if (length == 0 && initialValue) return initialValue
    else if (length == 0) throw 'Reduce of empty array with no initial value'
    else if (length == 1 && initialValue) return fn(initialValue, this[0])
    else if (length == 1) return this[0]
    else if (initialValue) current = fn(initialValue, this[0])
    else current = this[0]
    
    for (let i = 1; i < length; ++i) {
        current = fn(current, this[i])
    }

    return current
}