Question

Javascript objects can be used as maps. The following all is valid code:

var x = {};
x.a = 1;
x['b'] = 2; // the same as x.b = 2;
x[3] = 3; // x.3 won't work, but this syntax works fine. Also, x[3] == x['3'].
x['What, this works too?!?!?'] = 'Yup, it does!';

But today I tested another case which… seems to work, but raises some warning flags in my head because it looks… wrong:

x[null] = 42;

Now, it would be extremely cool if this worked as expected (I won’t have to rewrite a bunch of code then), but can I rely on it? Or maybe this is just some undocumented behavior which just happens to work in all modern browsers but might as well cease working on the next release of Google Chrome?

Answer 1

Anything between the property brackets is converted to a string. null becomes "null", which is a valid property.