[:] {
  _1;
  _2;
  ...
  _n;
}

_1, _2, _n

, .

break.

(., if...else, for, while). :

while (x < 10) {
  x++;
}

, .

() . , JavaScript . - JavaScript. - , , .

var

, var, . , , , , , , . , . " " , JavaScript, , , , C Java. :

var x = 1;
{
  var x = 2;
}
console.log(x); //  2

2, var x - , var x . C Java 1.

let const

, , let const :

let x = 1;
{
  let x = 2;
}
console.log(x); //  1

x = 2 , .

const:

const c = 1;
{
  const c = 2;
}
console.log(c); //  1    SyntaxError...

, const c = 2 SyntaxError: Identifier 'c' has already been declared ( 'c' ) .

• while
• if...else
• let