Javascript object initialization and evaluation order [duplicate]

Answer 1

They are evaluated in the order they are written.

Answer 2

See ECMAScript section 11.1.5 defining how the ObjectLiteral production is parsed.

In particular:

PropertyNameAndValueList , PropertyName : AssignmentExpression is evaluated as follows:

1. Evaluate PropertyNameAndValueList.

2. Evaluate PropertyName.

3. Evaluate AssignmentExpression.

...

Where (1) is a recursive definition.

This means the leftmost item in an object literal will get evaluated first, and so {foo: 2, bar: 1} is indeed spec-mandated.