Heterogenous reduce sum.

test.js

function heterogenous_sum_fold(prev, cur, I, a){
if( Object.prototype.toString.call( someVar ) === '[object Array]') { //if it's an array
    return prev +cur.reduce(heterogeneous_sum_fold);
   //apply this function recursively. 
} 
return prev + cur; // probably everything else. Might error. 
} 

Array.reduce(heterogeneous_sum_fold); //how to invoke