Boost your coding efficiency by learning how to measure performance in JavaScript! 🚀 In this video, I explain how to use the console.time() method to track the execution time of your code.

Whether you’re optimizing loops, debugging slow processes, or just curious about performance, this simple yet powerful tool is a must-know for every developer. Watch now to level up your JavaScript skills! 💻✨"

What are template literals?

Template literals are a feature in JavaScript, introduced with ES6, that allow you to create strings that are more flexible and powerful than traditional string concatenation. They are enclosed by backticks (`) instead of single (') or double (") quotes.


Key Features of Template Literals:


1. String Interpolation:
○ Allows embedding expressions directly within the string using the ${expression} syntax.

○ Example:


const name = 'John';
const age = 30;
const greeting = Hello, my name is ${name} and I am ${age} years old.;
console.log(greeting);

// Output: Hello, my name is John and I am 30 years old.




1. Multiline Strings:
○ Template literals can span multiple lines without needing escape characters (\n).
○ Example:


const multiline = `This is a string
that spans across
multiple lines.`;
console.log(multiline);


Output--





1. Expression Evaluation:
○ Any valid JavaScript expression can be included inside the ${} placeholder.
○ Example:


const a = 5;
const b = 10;
console.log(`The sum of ${a} and ${b} is ${a + b}.`);
// Output: The sum of 5 and 10 is 15.



2. Tagged Templates:
○ A way to process template literals with a function.
○ Example:


function tag(strings, ...values) {
return strings[0] + values.map((val) => val.toUpperCase()).join("");
}
const result = tag`Hello ${"world"}!`;
console.log(result);
// Output: Hello WORLD!



3. Dynamic HTML or Other Markup:
○ Useful for dynamically constructing HTML or other content.
○ Example:
const title = 'Welcome';
const content = <h1>${title}</h1>;
console.log(content);
Syntax:

string text
string text ${expression} string text


Template literals are especially useful for creating complex strings and enhancing code readability.

Here are 20 JavaScript multiple-choice interview questions along with answers:

---

### 1. What is the output of the following code?

javascript 
console.log(typeof null); 

- A. "null"
- B. "object"
- C. "undefined"
- D. "number"

Answer: B. "object"

---

### 2. Which of the following is not a primitive data type in JavaScript?
- A. Number
- B. Object
- C. String
- D. Boolean

Answer: B. Object

---

### 3. What is the correct syntax to create an array in JavaScript?
- A. var arr = {};
- B. var arr = [];
- C. var arr = new Array();
- D. Both B and C

Answer: D. Both B and C

---

### 4. Which of the following methods is used to add an element to the end of an array?
- A. push()
- B. pop()
- C. shift()
- D. unshift()

Answer: A. push()

---

### 5. What is the output of the following code?

javascript 
console.log(2 + "2"); 

- A. 22
- B. 4
- C. NaN
- D. Error

Answer: A. 22

---

### 6. How do you write an arrow function in JavaScript?
- A. function => () {}
- B. () => {}
- C. => function {}
- D. () -> {}

Answer: B. () => {}

---

### 7. What will `console.log([] == false)` output?
- A. true
- B. false
- C. undefined
- D. Error

Answer: A. true

---

### 8. Which keyword is used to declare a constant variable in JavaScript?
- A. let
- B. var
- C. constant
- D. const

Answer: D. const

---

### 9. What is the purpose of `isNaN()` in JavaScript?
- A. Check if a value is a number
- B. Check if a value is not a number
- C. Check if a value is undefined
- D. Check if a value is null

Answer: B. Check if a value is not a number

---

### 10. What does `==` compare in JavaScript?
- A. Value only
- B. Type only
- C. Value and type
- D. None of the above

Answer: A. Value only

---

### 11. Which of the following is used to stop event propagation?
- A. stopPropagation()
- B. preventDefault()
- C. return false;
- D. clearPropagation()

Answer: A. stopPropagation()

---

### 12. What is the purpose of `JSON.stringify()`?
- A. Convert a JSON string to an object
- B. Convert an object to a JSON string
- C. Parse a URL string
- D. None of the above

Answer: B. Convert an object to a JSON string

---

### 13. Which method is used to combine two or more arrays in JavaScript?
- A. concat()
- B. merge()
- C. join()
- D. add()

Answer: A. concat()

---

### 14. What is the output of the following code?

javascript 
console.log("5" - 2); 

- A. 3
- B. 52
- C. "5-2"
- D. Error

Answer: A. 3

---

### 15. Which of the following is a falsy value in JavaScript?
- A. 0
- B. ""
- C. null
- D. All of the above

Answer: D. All of the above

---

### 16. What is a closure in JavaScript?
- A. A function inside an object
- B. A function bundled with its lexical environment
- C. A block of code inside curly braces
- D. None of the above

Answer: B. A function bundled with its lexical environment

---

### 17. How can you check if a variable is an array?
- A. typeof variable === "array"
- B. Array.isArray(variable)
- C. variable instanceof Array
- D. Both B and C

Answer: D. Both B and C

---

### 18. What is the purpose of `setTimeout()`?
- A. Repeats execution of code at specified intervals
- B. Executes a function after a delay
- C. Stops the execution of code
- D. None of the above

Answer: B. Executes a function after a delay

---

### 19. What will `console.log(!!"")` output?
- A. true
- B. false
- C. undefined
- D. Error

Answer: B. false

---

### **20. Which JavaScript feature

allows functions to operate on objects irrespective of their type?**
- A. Closures
- B. Prototypes
- C. Polymorphism
- D. Hoisting

Answer: C. Polymorphism

---

1. What is the output of the following code?

   console.log(typeof null);
   

- A) "object"
- B) "null"
- C) "undefined"
- D) "boolean"

Answer: A) "object"

2. Which of the following is not a JavaScript data type?
- A) String
- B) Number
- C) Boolean
- D) Float

Answer: D) Float

3. What will the following code output?

   console.log(0 == '0');
   console.log(0 === '0');
   

- A) true, true
- B) true, false
- C) false, true
- D) false, false

Answer: B) true, false

4. **What is the purpose of the let keyword in JavaScript?**
- A) To declare a block-scoped variable
- B) To declare a global variable
- C) To declare a constant
- D) To declare a function
Answer: A) To declare a block-scoped variablele**
What will the following code output?t?**

   console.log(1 + "2" + "2");
   

- A) "122"
- B) "32"
- C) "14"
- D) "5"
Answer: A) "122"2"**
Which method is used to add an element to the end of an array?y?**
- A) push()
- B) pop()
- C) shift()
- D) unshift()

**Answer: A) push()**

7. **What is the output of the following code?**

   console.log(typeof NaN);
   

- A) "number"
- B) "NaN"
- C) "undefined"
- D) "Answer: A) "number") "number"**

8. **What does the this keyword refer to in a JavaScript method?**
- A) The function itself
- B) The global object
- C) The object that the method belongs to
- D) The paAnswer: C) The object that the method belongs tohod bWhat will the following code output?g code output?**

   console.log([] + []);
   

- A) "undefined"
- B) "null"
- C) ""
Answer: C) ""*AnsweWhich of the following is not a valid way to create a JavaScript object?Script object?**
- A) let obj = {};
- B) let obj = new Object();
- C) let obj = Object.create(null);
- D) let obj = new Object(null);

**Answer: D) let obj = new Object(null);**

11. **What is the output of the following code?**

    console.log(1 == true);
    console.log(0 == false);
    

- A) true, true
- B) true, false
- C) false, true
Answer: A) true, true*Answer: A) true, true**

12. **What is the purpose of the bind() method in JavaScript?**
- A) To bind a function to an object
- B) To bind an event to a function
- C) To bind a variable to a function
- D) To bind a Answer: A) To bind a function to an objectnd a fWhat will the following code output?the following code output?**

    console.log(typeof undefined);
    

- A) "undefined"
- B) "null"
- C) "objeAnswer: A) "undefined" **AnWhich of the following is not a JavaScript framework or library?ript framework or library?**
- A) React
- B) Angular
- Answer: D) Djangoo

What is the output of the following code?put of the following code?**

    console.log(2 + "2" - 1);
    

- A) "21"
- B) "22"
Answer: C) 21 D) 3

**Answer: C) 21**

16. **What is the purpose of the map() method in JavaScript?**
- A) To create a new array by applying a function to each element of an existing array
- B) To filter elements of an array based on a condition
- C) To reduce an array to a single value
- D) To sorAnswer: A) To create a new array by applying a function to each element of an existing arrayh elemWhat will the following code output?ill the following code output?**

    console.log(typeof []);
    

- A) "array"
- B) "object"
- C) "Answer: B) "object"ll"

Which of the following is not a valid JavaScript loop?s not a valid JavaScript loop?**
- A) for
- B) while
- C) do...while
- D) foreach

**Answer: D) foreach**