CODING EXERCISES TEST YOUR SKILLS
π Unraveling the Mysteries of JavaScript Hoisting! π
Set of 10 engaging exercises focused on demystifying the concept of hoisting in JavaScript. π»π§
Hoisting is a unique behavior in JavaScript where variable and function declarations are moved to the top of their containing scope during compilation. Understanding this concept is crucial for writing clean, error-free code. ππ¨βπ»π©βπ»
Here’s a glimpse of what you’ll explore:
- Variable Hoisting with var
- Function Declaration Hoisting
- Understanding Temporal Dead Zone with let and const
- Hoisting Inside Function and Block Scopes
- Hoisting Differences Between Function Expressions and Declarations
- The Intricacies of Hoisting in Loops
Whether you are a beginner trying to grasp JavaScript fundamentals or a seasoned developer brushing up your skills, these exercises offer valuable insights into how JavaScript interprets your code. ππΌ
Exercise 1: Variable Hoisting with var
Problem Statement:
Demonstrate variable hoisting by using a variable before it is declared with var.
Hint/Explanation:
In JavaScript, variable declarations (but not initializations) are hoisted to the top of their scope.
Solution:
console.log(myVar); // undefined
var myVar = 5;
Exercise 2: Function Hoisting
Problem Statement:
Call a function before it is declared and observe the behavior.
Hint/Explanation:
Function declarations are hoisted to the top of their enclosing scope.
Solution:
myFunction(); // “Hello, world!”
function myFunction() {
console.log(“Hello, world!”);
}
Exercise 3: Variable Hoisting with let
Problem Statement:
Try to use a variable declared with let before its declaration and observe the behavior.
Hint/Explanation:
Variables declared with let are hoisted but not initialized. Accessing them before declaration results in a ReferenceError.
Solution:
// console.log(myLetVar); // ReferenceError: Cannot access ‘myLetVar’ before initialization
let myLetVar = 3;
Exercise 4: Hoisting Inside a Function
Problem Statement:
Demonstrate hoisting behavior within a function scope.
Hint/Explanation:
Variables declared with var are hoisted to the top of their function scope, not the block scope.
Solution:
function hoistTest() {
if (true) {
var hoisted = “I’m hoisted to the function scope!”;
}
console.log(hoisted); // “I’m hoisted to the function scope!”
}
hoistTest();
Exercise 5: Temporal Dead Zone
Problem Statement:
Illustrate the Temporal Dead Zone (TDZ) with a let variable.
Hint/Explanation:
The TDZ is the time between entering the scope and the declaration where the variable cannot be accessed.
Solution:
function tdzDemo() {
// console.log(aLetVar); // ReferenceError: Cannot access ‘aLetVar’ before initialization
let aLetVar = 10;
console.log(aLetVar); // 10
}
tdzDemo();
Exercise 6: Hoisting with Function Expressions
Problem Statement:
Try calling a function expression before itβs defined.
Hint/Explanation:
Function expressions are not hoisted like function declarations.
Solution:
// myFuncExp(); // TypeError: myFuncExp is not a function
var myFuncExp = function() {
console.log(“This is a function expression!”);
};
Exercise 7: Hoisting in Block Scope
Problem Statement:
Show how var behaves differently from let and const in a block scope.
Hint/Explanation:
var is hoisted to the function scope, while let and const adhere to the block scope.
Solution:
{
var varVariable = “I’m hoisted to the function scope”;
let letVariable = “I’m confined to this block”;
}
console.log(varVariable); // “I’m hoisted to the function scope”
// console.log(letVariable); // ReferenceError: letVariable is not defined
Exercise 8: Hoisting and Variable Redefinition
Problem Statement:
Show how redefining a variable with var can lead to unexpected behavior due to hoisting.
Hint/Explanation:
Redefining a variable with var in the same scope is a legal operation but can lead to confusing code due to hoisting.
Solution:
var x = 5;
function redefVar() {
x = 10; // Refers to the global x
if (false) {
var x; // This declaration is hoisted
}
return x;
}
console.log(redefVar()); // 10
console.log(x); // 5
Exercise 9: Function Declaration vs. Expression
Problem Statement:
Compare hoisting behavior between function declarations and expressions.
Hint/Explanation:
Function declarations are hoisted, but function expressions (assigned to variables) are not.
Solution:
console.log(funcDecl()); // “Function declaration”
// console.log(funcExpr()); // TypeError: funcExpr is not a function
function funcDecl() {
return “Function declaration”;
}
var funcExpr = function() {
return “Function expression”;
};
Exercise 10: Hoisting in Loops
Problem Statement:
Illustrate how hoisting affects variables declared with var in a loop.
Hint/Explanation:
Variables declared with var in loops are hoisted to the top of the function or global scope.
Solution:
for (var i = 0; i < 3; i++) {
// loop body
}
console.log(i); // 3, because i is hoisted to the global scope
These exercises provide a mix of practical and theoretical understanding of hoisting in JavaScript, demonstrating its effects in various scenarios. This knowledge is crucial for writing predictable and error-free JavaScript code.
Dive into these exercises, challenge yourself, and share your thoughts or solutions. Let’s engage in a fruitful discussion about how hoisting affects our JavaScript code. If you have any questions or additional insights, feel free to comment below. Happy coding! ππ
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