How to convert between binary, decimal, hex, octal numbers in JavaScript

Do you want to convert a number from one base to another? Just keep reading this article.

Getting started

In JavaScript, a number has a super useful method toString(radix) that converts its value in decimal to a string of that number in the specified radix.

On the contrary, the parseInt(string, radix) function converts a string in the specified radix to a decimal number.

Go ahead!

Decimal to binary

const number = 123;
number.toString(2); // '1111011'

Decimal to hex

const number = 123;
number.toString(16); // '7b'

Decimal to octal

const number = 123;
number.toString(8); // '173'

Binary to decimal

parseInt('1111011', 2); // 123

Hex to decimal

parseInt('7b', 16); // 123

Octal to decimal

parseInt('173', 8); // 123

Universal conversion function

To convert a number in decimal to other bases and vice versa are very straightforward. To convert a number between other bases, such as binary to hex, requires a little more effort. But do not worry, it is not too hard to implement.

There are 2 steps:

Convert the input number (or string) from the source base to decimal
Convert that decimal number to the destination base

const convertNumberBetweenBases = ({ number, fromRadix, toRadix }) => {
  const decimal = parseInt(number, fromRadix);
  const toRadixNumber = decimal.toString(toRadix);
  return toRadixNumber;
};

Let’s try with some examples!

Binary to hex

convertNumberBetweenBases({
  number: '1111011',
  fromRadix: 2,
  toRadix: 16,
});
// '7b'

Binary to octal

convertNumberBetweenBases({
  number: '1111011',
  fromRadix: 2,
  toRadix: 8,
});
// '173'

Hex to binary

convertNumberBetweenBases({
  number: '7b',
  fromRadix: 16,
  toRadix: 2,
});
// '1111011'

Hex to octal

convertNumberBetweenBases({
  number: '7b',
  fromRadix: 16,
  toRadix: 8,
});
// '173'

Octal to binary

convertNumberBetweenBases({
  number: '173',
  fromRadix: 8,
  toRadix: 2,
});
// '1111011'

Octal to hex

convertNumberBetweenBases({
  number: '173',
  fromRadix: 8,
  toRadix: 16,
});
// '7b'

Conclusion

The universal conversion function is useful, right?

In this article, you have seen how to use the toString() method to convert a number to a string. If you want to see more other ways, you can read the article How to convert a number to a string in JavaScript.

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