Gitter/developers

@Srinath-V-S Before I answer your question, let me give you a few tips. Firstly, in the toBits function, you're constructing a large object and then throwing away all of it except for one of its properties. You could avoid this, performing only the calculation you need, by using a switch statement like this:

function toBits(data, unit) {
    switch(unit) {
    case 'b': return data;
    case 'kb': return data * 1000;
    case 'mb': return data * 1000 * 1000;
    case 'gb': return data * 1000 * 1000 * 1000
    case 'tb': return data * 1000 * 1000 * 1000 * 1000;
    case 'B': return data * 8;
    case 'KB': return data * 8000;
    case 'MB': return data * 8000 * 1000;
    case 'GB': return data * 8000000 * 1000;
    case 'TB': return data * 8000000 * 1000 * 1000;
    }
}

However, you can still do better based on the next two tips.

Secondly, I recommend using consistent names for the units. In response you're writing the names in full, while in toBits, you're using abbreviations. On top of that, those abbreviations aren't consistent with the SI prefixes. It's "kB", not "KB", and "Mb"/"Gb"/"Tb", not "mb"/"gb"/"tb". Using consistent names makes it easier for yourself to predict which name you should be using in your code, and also helps with the next tip I'm about to give.

Thirdly, note that you're repeating the numbers in both functions. You can share them in a common variable so you don't have to repeat yourself:

const unitFactors = {
    b: 1,
    kb: 1000,
    Mb: 1000 * 1000,
    Gb: 1000 * 1000 * 1000,
    Tb: 1000 * 1000 * 1000 * 1000,
    B: 8,
    kB: 8 * 1000,
    MB: 8 * 1000 * 1000,
    GB: 8 * 1000 * 1000 * 1000,
    TB: 8 * 1000 * 1000 * 1000 * 1000,
};

function response(bits) {
    const obj = {};
    for (let unit in unitFactors) {
        obj[unit] = bits / unitFactors[unit];
    }
    return obj;
}

function toBits(value, unit) {
    return value * unitFactors[unit];
}

This has the added benefit that if you want to show a dropdown with units, you can just use Object.keys(unitFactors) (or _.keys(unitFactors) if using Underscore or Lodash) to get an array with all the unit names. Also, if you want to display full unit names somewhere, you can just use a second mapping from abbreviations to full names:

const unitFullNames = {
    b = 'bit',
    kb = 'kilobit',
    Mb = 'megabit',
    Gb = 'gigabit',
    Tb = 'terabit',
    B = 'byte',
    kB = 'kilobyte',
    MB = 'megabyte',
    GB = 'gigabyte',
    TB = 'terabyte',
};

Now to answer your original question. You may have already realised that if the user inputs a value and a unit, you can obtain an object with equivalent values in all units (including the one the user entered) with the expression response(toBits(value, unit)). If I understood your question correctly, you want to remove the unit that the user entered from this object. A simple way to do that is with the delete operator:

const otherUnits = response(toBits(value, unit));
delete otherUnits[unit];

Underscore has a helper function omit that lets you achieve the same thing in a single expression:

const otherUnits = _.omit(response(toBits(value, unit)), unit);

I hope this helps!