console.error

/**
* Let's throw an actual error if something is not an integer.
* @param {[type]} x [description]
* @param {[type]} y [description]
*/

function add(x,y){
    if( isNaN(x) || isNaN(y) ){
        throw new Error("OMG ERROR: I need numbers only k");
    } else {

        // ensure we're adding numbers, not concatenating numeric strings
        return (x * 1) + (y * 1);
    }
}

var a;

try {
    a = add(9);
} catch(e) {
    // throw an actual error here.
    console.error( e.message );
}