const

const number = 42;

try {
  number = 99;
} catch (err) {
  console.log(err);
  // Expected output: TypeError: invalid assignment to const 'number'
  // (Note: the exact output may be browser-dependent)
}

console.log(number);
// Expected output: 42

    const name1 = value1 [, name2 = value2 [, ... [, nameN = valueN]]];

// :       ,
//      .

// MY_FAV     7 
const MY_FAV = 7;

//  
MY_FAV = 20;

// 7 
console.log("my favorite number is: " + MY_FAV);

//      - Uncaught SyntaxError: Identifier 'MY_FAV' has already been declared
const MY_FAV = 20;

// MY_FAV       .
var MY_FAV = 20;

//   
let MY_FAV = 20;

//     
if (MY_FAV === 7) {
  //    MY_FAV    
  // (let const        )
  let MY_FAV = 20;

  // MY_FAV  20
  console.log("my favorite number is " + MY_FAV);

  //      .
  var MY_FAV = 20;
}

// MY_FAV  7
console.log("my favorite number is " + MY_FAV);

// const     
const FOO;

// const   
const MY_OBJECT = { key: "value" };

//    
MY_OBJECT = { OTHER_KEY: "value" };

//     .
//     
MY_OBJECT.key = "otherValue"; //      Object.freeze()   

//   
const MY_ARRAY = [];
//     
MY_ARRAY.push("A"); // ["A"]
//       
MY_ARRAY = ["B"];