1️⃣ Variables
Q: What’s the difference between var, let, and const?
A:
•
var is function-scoped and hoisted (can be redeclared).•
let is block-scoped and cannot be redeclared in the same scope.•
const is also block-scoped but must be initialized and cannot be reassigned.let x = 10;
x = 20; // ✅ allowed
const y = 5;
y = 10; // ❌ Error: Assignment to constant variable
2️⃣ Functions
Q: What are the different ways to define a function in JavaScript?
A:
• Function Declaration:
function greet(name) {
return Hello, ${name};
}
• Function Expression:
const greet = function(name) {
return Hello, ${name};
};
• Arrow Function:
const greet = name => Hello, ${name};
Q: What is the difference between a regular function and an arrow function?
A: Arrow functions have a shorter syntax and do not bind their own
this, making them ideal for callbacks.3️⃣ Arrays
Q: How do you iterate over an array in JavaScript?
A:
• Using
for loop: for (let i = 0; i < arr.length; i++) {
console.log(arr[i]);
}
• Using
forEach:arr.forEach(item => console.log(item));
• Using
map (returns a new array):const doubled = arr.map(x => x * 2);
Q: How do you remove duplicates from an array?
A:
const unique = [...new Set(arr)];
4️⃣ Loops
Q: What are the different types of loops in JavaScript?
A:
•
for loop•
while loop•
do...while loop•
for...of (for arrays)•
for...in (for objects)Q: What’s the difference between
for...of and for...in? A:
•
for...of iterates over values (arrays, strings).•
for...in iterates over keys (objects).5️⃣ Conditionals
Q: How does the
if...else statement work in JavaScript? A: It executes code blocks based on boolean conditions.
if (score >= 90) {
console.log("A");
} else if (score >= 80) {
console.log("B");
} else {
console.log("C or below");
}
Ternary Operator:
let result = score >= 60 ? "Pass" : "Fail";
Q: What’s the difference between
== and ===? A:
•
== compares values with type coercion.•
=== compares both value and type (strict equality).'5' == 5 // true
'5' === 5 // false
Bonus: Common Tricky Questions
Q: What is hoisting in JavaScript?
A: Hoisting is JavaScript’s behavior of moving declarations to the top of the scope. Only declarations are hoisted, not initializations.
Q: What is the difference between
null and undefined? A:
•
undefined: A variable declared but not assigned.•
null: An intentional absence of value.💬 Double Tap ♥️ For More