How to convert binary fraction to decimal

Question

Javascript has the function parseInt() which can help convert integer in a binary form into its decimal equivalent:

parseInt(\"101\", 2) // 5
         


        

Answer 1

TL;DR:

const convert = (s, b) => (+((s = s.toString().trim().split("."))[0][0] !== "-") || -1) * ((parseInt(s[0].replace("-", ""), (b = +b || 2))) + (s[1].split("").reduceRight((n, d) => (n + parseInt(d, b)) / b, 0)));

---

Nina Scholz has a nice example, but it doesn't work with negative numbers (plus other issues).
So, this is an improved one:

/**
 * @param {string} input
 * @param {number} [base]
 * @returns {number}
 */
function convert(input, base = 2) {
    const [ integerRaw, decimalRaw = "" ] = input.toString().trim().split(".");

    const integer = parseInt(integerRaw.replace("-", ""), base);
    const decimal = decimalRaw.split("").reduceRight((sum, num) => (sum + parseInt(num, base)) / base, 0);

    return (integerRaw.startsWith("-") ? -1 : 1) * (integer + decimal);
}

convert("1100.0011"); // 12.1875
convert("-1100.0011"); // -12.1875
convert("-Z.ZZZ", 36); // -35.99997856652949

As I know, JavaScript doesn't provide such built-in functionality.