Just had a quick question about why a certain order of assignment works and another doesn't. I wanted to create a simple "inherit" / "copy" function (just for testing it) that copies properties from one object to another: var cat = { tail:"yes", hairy:"yes, hairy" }; var dog = { sick:"extremely ill"}; function inherit(obj1, obj2) { for (var p in obj1) { obj2[p] = obj1[p]; // this works, but "obj1[p] = obj2[p];" doesn't. Why?? } } inherit(cat, dog); console.log(dog.tail);