Javascript unexpected behaviors

Question

there are some behaviors I don't understand in Javascript :

1. Why console.log(011666) logged 5046 ?
2. Why typeof typeof 500 logged string ?

Answer 1

1. A number starting with 0 is interpreted as octal number. A simpler example:

console.log(010);

2. typeof 500 returns a string 'number'. The type of a string 'number' is 'string'.

console.log(typeof 500);
console.log(typeof 'number');