[VeejayRampay]

Ruby: obj.each{|k,v| ...}

Sure you can do it in JS, but calling Object.keys then forEach (in whose closure you'll still have to reference obj[key] by the way) still doesn't feel optimal.

[seangrogg]

In which case, if you really can't live without it, just attach it to the prototype.

Object.prototype.each = function(k,v){ //... }

[SerpentJoe]

I would argue that automatically adding methods to a user-created object isn't optimal either.