reducer$1$

If this function is passed to reduce, any non$-$numeric values in the array will be skipped and the sum of only the numeric values in the array will be returned.

If all the values in the array are non$-$numeric, then the value $0$ will be returned.

reducer$2$

If this function is passed to reduce and the array contains any non$-$numeric values, this function will throw the exception TypeError.

Otherwise, the sum of all the values in the array will be returned.

To throw the exception TypeError with the message $\text{'}$My error message' you can use the statement throw new TypeError$(\text{'}$My error message'$).$ See TypeError on MDN for more discussion of this exception.