Variable assignment inside an 'if' condition in JavaScript

Question

How does the below code execute?

if(a=2 && (b=8))
{
    console.log(a)
}

OUTPUT

a=8

Answer 1

To understand what is going on, refer to the operator precedence and associativity chart. The expression a = 2 && (b = 8) is evaluated as follows:

• && operator is evaluated before = since it has higher priority
  • the left hand expression 2 is evaluated which is truthy
  • the right hand expression b = 8 is evaluated (b becomes 8 and 8 is returned)
  • 8 is returned
• a = 8 is evaluated (a becomes 8 and 8 is returned)

Finally, the if clause is tested for 8.

Note that 2 does not play any role in this example. However, if we use some falsy value then the result will be entirely different. In that case a will contain that falsy value and b will remain untouched.