Are elements of Javascript arrays processed in a defined order?

Question

For example:

var a = [];
function p(x) { a.push(x); }

[[p(1),p(2)],p(3),[p(4),[p(5)]],p(6)]

a == [1,2,3,4,5,6] // Always true?

Is 'a == [1,2,3,4,5,6]' defined behavior? Can it be relied upon?

Answer 1

Are elements of Javascript arrays processed in a defined order?

Yes they are.

Is 'a == [1,2,3,4,5,6]' defined behavior? Can it be relied upon?

No, the equals operator performs referential equality when comparing object.

Answer 2

Short answer: "Yes".

Longer answer: Your question is actually about JavaScript statements in general and not Arrays. The code you posted ([[p(1),p(2)],p(3),[p(4),[p(5)]],p(6)]) is not an Array, it is a statement that returns an Array whilst also populating an Array. JavaScript statements are executed according to the rules of operator precedence.