# Number Data Type

**Data Types: Numbers**

### In JavaScript, What is the Number object?

**View Answer:**

**Interview Response:**The Number object is a built-in object in JavaScript that represents numerical values and provides methods for working with numbers.

**Technical Response:**In JavaScript, the Number object is a wrapper object that allows you to work with numerical values. The Number object can be created using the Number() constructor, but it's often not necessary because JavaScript automatically converts number literals and variables to instances of the Number object when necessary.

**Code Example:**

`let num = new Number(10);`

However, you generally don't need to explicitly create Number objects in this way. Instead, you can just work with number primitives, like so:

`let num = 10;`

JavaScript will automatically convert `num`

to a Number object when you call methods on it. For example:

`let num = 10;`

console.log(num.toFixed(2)); // "10.00"

In this case, JavaScript temporarily converts the number primitive `10`

to a Number object so that the `toFixed`

method can be used.

The Number object also has properties for numerical constants, such as `Number.MAX_VALUE`

, `Number.MIN_VALUE`

, `Number.NaN`

(representing "Not a Number"), `Number.POSITIVE_INFINITY`

, and `Number.NEGATIVE_INFINITY`

.

Finally, note that while the Number object is useful, using number primitives is generally more efficient. You should avoid using the Number constructor unless necessary because creating Number objects can slow down execution speed.

### What are the two primitive number data types in JavaScript?

**View Answer:**

**Interview Response:**There are two primitive number data types including Number for integers and floating-point values, and BigInt for arbitrarily large integers.

### In what format are regular numbers stored in JavaScript?

**View Answer:**

**Interview Response:**JavaScript stores regular numbers using the double-precision 64-bit binary format IEEE 754, which represents floating-point numbers and integers within its range.

### Can you explain the limitations of BigInt in JavaScript?

**View Answer:**

**Interview Response:**BigInt has some limitations, including an inability to mix with regular numbers in operations, incompatibility with some built-in methods like Math functions, and a lack of support in JSON.

### In JavaScript, Is there a safe way to separate large number groups like 1,000,000,000 and maintain a formal format?

**View Answer:**

**Interview Response:**Yes, we can use an underscore to ensure that the number maintains its primitive format.

**Technical Response:**The most common way to safely separate number groups without using a comma (which would cause an error) and keep its primitive format. We use an underscore (syntactic sugar) to ensure that the number maintains its primitive format. However, there are easier ways to propagate large numbers in most programming languages.

**Code Example:**

`let billion = 1_000_000_000;`

console.log(typeof billion); // returns number and maintains its primitive

let billions = 2,000,000,000;

console.log(typeof billons) // Uncaught SyntaxError: Unexpected number

### What is the most straightforward approach to avoid writing large numerical sequences like 1,000,000,000?

**View Answer:**

**Interview Response:**To avoid writing large numerical sequences, we can use e-notation (1e9 for 1,000,000,000) or store the value in a variable with a descriptive name.

**Code Example:**

`let billion = 1e9; // 1 billion, literally: 1 and 9 zeroes`

console.log( 7.3e9 ); // 7.3 billions (same as 7300000000 or 7_300_000_000)

// In other words, e multiplies the number by 1 with the given zeroes count.

// 1e3 = 1 * 1000 // e3 means *1000

// 1.23e6 = 1.23 * 1000000 // e6 means *1000000

// Now let’s write something very small as a regular number.

// Say, 1 microsecond (one millionth of a second):

let ms = 0.000001;

// Using "e" can help. If we’d like to avoid writing the zeroes explicitly

let ms = 1e-6; // six zeroes to the left from 1

### Can you explain what the exponential notation is used for in JavaScript?

**View Answer:**

**Interview Response:**Exponential notation or e-notation is used to represent very large or very small numbers more concisely, by using a shortened form of scientific notation, using "e" to indicate the power of 10.

### In exponential notation, What happens when the minus sign precedes a number in JavaScript, and how does it affect numbers expressed?

**View Answer:**

**Interview Response:**In JavaScript, placing a minus sign before a number negates its value. When used with numbers in exponential notation, it negates the exponent, effectively making the number smaller if it was positive, or larger if it was negative.

**For example, -1e3 is equivalent to -1000 or 1e-3 is equivalent to 0.001**

**Code Example:**

`console.log(1e-9); // 1e-9 is 0.000000001; the minus sign applies to the exponent`

console.log(-1e9); // -1e9 is - 1000000000.0; minus sign applies to the number itself.

### Which numeral systems are utilized in JavaScript for character encoding, color representation, and base representation purposes?

**View Answer:**

**Interview Response:**JavaScript uses the UTF-16 encoding for character representation, hexadecimal notation for color representation, and supports base 10 and base 16 (hexadecimal) representation of numbers.

**Code Example:**

`console.log(0xff); // 255`

console.log(0xFF); // 255 (the same, case doesn't matter)

// Binary and octal numeral systems

let a = 0b11111111; // binary form of 255

let b = 0o377; // octal form of 255

console.log(a == b); // true, the same number 255 at both sides

Hexadecimal is base 16, The decimal is base 10, Octal is base 8, and Binary is base 2.

### What is the most common numeral system used in JavaScript?

**View Answer:**

**Interview Response:**The most common numeral system used in JavaScript is Base 10, which is the decimal system used for representing ordinary numbers.

### Is there a method in JavaScript that returns a string representation of a number within a given base?

**View Answer:**

**Interview Response:**Yes, the toString(base) method in JavaScript returns a string representation of a number in a given base. It takes an optional argument to specify the base.

**Code Example:**

`let num = 255;`

console.log(num.toString(16)); // ff

console.log(num.toString(2)); // 11111111

### What is the default base in JavaScript?

**View Answer:**

**Interview Response:**JavaScript is base 10 by default, but the base can vary from 2 to 36 based on your use case.

**Code Example:**

`console.log(parseInt('-15', 2)); // returns -15`

console.log(parseInt('-15', 16)); // returns -21

// parseInt() syntax: parseInt(‘string’, [radix]);

### What is the difference between regular numbers and BigInts in JavaScript?

**View Answer:**

**Interview Response:**Regular numbers are 64-bit floating-point values that can represent integers and decimals up to a certain precision, while BigInts are a built-in type for representing integers of arbitrary precision.

### What is the difference between Number() and new Number()?

**View Answer:**

**Interview Response:**Number() is a function that converts a value to a number, while new Number() is a constructor that creates a Number object. The former returns a primitive value, the latter an object.

### Should we use the new Number() constructor in JavaScript?

**View Answer:**

**Interview Response:**No, it's generally not recommended to use the new Number() constructor in JavaScript, as it can lead to unexpected results and is less efficient than using the Number() function.

### What is the purpose of the toFixed() method?

**View Answer:**

**Interview Response:**The toFixed() method is used in JavaScript to format a number with a specified number of digits after the decimal point and return it as a string.

### What is the purpose of the toString() method in relation to numbers?

**View Answer:**

**Interview Response:**The toString() method in JavaScript is used to convert a number to a string representation, allowing it to be displayed as text or manipulated in various ways.

### What are some solutions to deal with the issue of imprecise numbers in JavaScript, and how can they be implemented?

**View Answer:**

**Interview Response:**One solution is to use a library like BigNumber.js, which provides arbitrary-precision arithmetic. Another is to use integer math where possible, or use rounding methods like Math.round().

### What is the function of the valueOf() method in JavaScript?

**View Answer:**

**Interview Response:**The valueOf() method in JavaScript returns the primitive value of a specified object, commonly used with number, string, and boolean objects.

### What is the difference between Number.isNaN() and isNaN()?

**View Answer:**

**Interview Response:**In JavaScript, Number.isNaN() strictly checks if a value is NaN, while isNaN() first attempts to convert the value to a number, resulting in potential type coercion and false positives. Therefore, Number.isNaN() is more reliable for checking if a value is NaN.

### What is the purpose of the Number.isFinite() method?

**View Answer:**

**Interview Response:**The purpose of the Number.isFinite() method in JavaScript is to determine if a given value is a finite number, excluding Infinity, -Infinity, and NaN.

### What is the purpose of the Number.parseFloat() method?

**View Answer:**

**Interview Response:**The purpose of the Number.parseFloat() method in JavaScript is to parse a string argument and return a floating-point number or NaN if parsing fails.

### What is the purpose of the Number.parseInt() method?

**View Answer:**

**Interview Response:**The purpose of the Number.parseInt() method in JavaScript is to parse a string argument and return an integer, or NaN if parsing fails, allowing for optional radix specification.