dfcreative/mutype

//speedy implementation of `in`
//NOTE: `!target[propName]` 2-3 orders faster than `!(propName in target)`
module.exports = function(a, b){
    if (!a) return false;

    //NOTE: this causes getter fire
    if (a[b]) return true;

    //FIXME: why in is better than hasOwnProperty? Something with prototypes. Show a case.
    return b in a;
    // return a.hasOwnProperty(b);
}