JavaScript program to take in a binary number as a string and returns its numerical equivalent in base 10

We are required to write a JavaScript function that takes in a binary number as a string and returns its numerical equivalent in base 10. Therefore, let's write the code for the function.

This one is quite simple, we iterate over the string using a for loop and for each passing bit, we double the number with adding the current bit value to it like this ?

Example

const binaryToDecimal = binaryStr => {
   let num = 0;
   for(let i = 0; i 

Output

The output in the console will be ?

13
104
21


How It Works

The algorithm processes each binary digit from left to right. For each digit, it doubles the current result (equivalent to left-shifting in binary) and adds the digit value (0 or 1). This effectively builds the decimal value bit by bit.

Using Built-in parseInt() Method

JavaScript provides a built-in method to convert binary strings to decimal using parseInt() with base 2:

const binaryToDecimalBuiltIn = binaryStr => {
   return parseInt(binaryStr, 2);
};

console.log(binaryToDecimalBuiltIn('1101'));
console.log(binaryToDecimalBuiltIn('1101000'));
console.log(binaryToDecimalBuiltIn('10101'));


13
104
21


Comparison

Conclusion

Both methods effectively convert binary strings to decimal. The manual approach helps understand the conversion process, while parseInt() provides a cleaner, production-ready solution.