Addition assignment += behavior in expression

Question

Recently I came across this question: Assignment operator chain understanding.

While answering this question I started doubting my own understanding of the behavior of t

Answer 1

It just uses a variation of order of ops.

If you need a reminder of order of ops:

PEMDAS:

P = Parenthesis

E = Exponents

MD = Multiplication/Division

AS = Addition/Subtraction

The rest left to right.

This variation just is read left to right, but if you see a parenthesis do everything inside it, and replace it with a constant then move on.

First ex:

var b = (a+=(a+=a))

var b = (1+=(1+=1))

var b = (1+=2)

var b = 3

Second ex:

var b = (a+=a)+(a+=a)

var b = (1+=1)+(a+=a)

var b = 2 + (2+=2)

var b = 2 + 4

var b = 6

var a = 1
var b = (a += (a += a))
console.log(b);

a = 1
b = (a += a) + (a += a)
console.log(b);

a = 1
b = a += a += a;
console.log(b);

The last one b = a += a += a since there are no parenthesis, it automatically becomes b = 1 += 1 += 1 which is b = 3