const

Examples

A constant:

const pi = 3.14;
 
console.log(pi * 2);

Output:

6.28

Reassigning fails, changing the object works:

const user = { name: 'Anna' };
user.name = 'Oleg';
console.log(user.name);
 
try {
  user = {};
} catch (error) {
  console.log(error.name);
}

Output:

Oleg
TypeError

Notes

const forbids assigning a new value to the variable but does not make the object immutable. For that there is Object.freeze().

Declare variables with const by default and with let only if the value will change.