gistfile1.js

var prefixes = [
    {
        prefix: "",
        name: ""
    },
    {
        prefix: "Ki",
        name: "kibi"
    },
    {
        prefix: "Mi",
        name: "mebi"
    },
    {
        prefix: "Gi",
        name: "gibi"
    },
    {
        prefix: "Ti",
        name: "tebi"
    },
    {
        prefix: "Pi",
        name: "pebi"
    },
    {
        prefix: "Ei",
        name: "exbi"
    }
];

const GROUP = 1024;

function binaryUnitFormat(x, unit) {
    var index = 0;
    var xnew = x;
    
    while (xnew >= GROUP && index < prefixes.length - 1) {
        xnew /= GROUP;
        index++;
    }
    
    var result = {};
    result.mag = xnew;
    result.unit = prefixes[index].prefix + unit;
    
    return result;
}

var count = 1371;
var unit = "B";
var formatted = binaryUnitFormat(count, unit);

print(count + " " + unit + " is about " + formatted.mag.toFixed(2) + " " + formatted.unit);