That one is rather simple to break. console.log(add({a:"1", b:2})) //12 console.log(_add({a:"1", b:2})) //21 So to make the code break with the change

That one is rather simple to break. console.log(add({a:"1", b:2})) //12 console.log(_add({a:"1", b:2})) //21 So to make the code break with the change to _add, I can just do: if(add({a:"1", b:2}) != 12) boom()