5.6 Let¶

Let Declaration¶

Task 1: Declare a variable called num, and set its value to 10.

var num = 10;

console.log(num);

The result is: 10

Task 2: Re-do task 1, and re-declare num with the let keyword.

let num = 10;

console.log(num);

The result is: 10

Task 3: Refer to task 2; assign the value of 20 to the num variable.

let num = 10;

num = 20;
console.log(num);

The result is: 20

Task 4: Declare name variable with the let keyword. Assign "Ali" to it.

let name;

name = "Ali";
console.log(name);

The result is: Ali

Task 5: Declare type variable with the let keyword. Assign true to it.

let type;

type = true;
console.log(type);

The result is: true

Task 6: Re-declare the variable myVar with the var keyword. Assign "hello" to it.

var myVar = "Bye";

var myVar = "Hello";
console.log(myVar);

The result is: Hello

Task 7: Re-declare the variable myVar with let keyword. Assign "hello" to it.

let myVar = "Bye";

let myVar = "Hello";
console.log(myVar);

The result is: Uncaught SyntaxError: Identifier 'myVar' has already been declared

Task 8: Re-declare the variable secret with let keyword. Assign "Top Secret" to it.

let secret = "Not a secret";

let secret = "Top Secret";
console.log(secret);

The result is: Uncaught SyntaxError: Identifier 'secret' has already been declared

Let Scope¶

Task 9: Log the value of myVar outside the function.

function myFunc(){
  var myVar = 5;
  return myVar;
}

console.log(myVar);

The result is: Uncaught ReferenceError: myVar is not defined

Task 10: Log the value of myVar outside the function.

function myFunc(){
  let myVar = 5;
  return myVar;
}

console.log(myVar);

The result is: Uncaught ReferenceError: myVar is not defined

Task 11: Log the value of myVar outside the curly brackets.

{
  var myVar = "I am inside a block";
}

console.log(myVar);

The result is: I am inside a block

Task 12: Log the value of myVar outside the curly brackets.

{
  let myVar = "I am inside a block";
}

console.log(myVar);

The result is: Uncaught ReferenceError: myVar is not defined

Task 13: Log the value of myBlockVar variable outside the if statement.

if(true){
  var myBlockVar = true;
}

console.log(myBlockVar);

The result is: true

Task 14: Log the value of myBlockVar variable outside the if statement.

if(true){
  let myBlockVar = true;
}

console.log(myBlockVar);

The result is: Uncaught ReferenceError: myBlockVar is not defined

Let & Window¶

Task 15: Declare abc variable with the var keyword. Set the value of abc to 1. Log window.abc in the console.

var abc;

abc = 1;
console.log(window.abc);

The result is: 1

Task 16: Declare abc variable with the let keyword. Set the value of abc to 1. Log window.abc in the console.

let abc;

abc = 1;
console.log(window.abc);

The result is: undefined

Task 17: Declare greeting variable with the var keyword. Set the value of greeting to "Hello everyone". Log window.greeting in the console.

var greeting;

greeting = "Hello everyone";
console.log(window.greeting);

The result is: Hello everyone

Task 18: Declare greeting variable with the let keyword. Set the value of greeting to "Hello everyone". Log window.greeting in the console.

let greeting;

greeting = "Hello everyone";
console.log(window.greeting);

The result is: undefined

Let Initialization¶

Task 19: Access the variable myVar before it is declared.

console.log(myVar);

var myVar = 5;

The result is: undefined

Task 20: Access the variable myVar before it is declared.

console.log(myVar);

let myVar = 5;

The result is: Uncaught ReferenceError: Cannot access 'myVar' before initialization