Remove current behavior of Big(undefined)

[fisker]

if the argument is undefined, then a new Big constructor will be returned

https://mikemcl.github.io/big.js/#big

It's too dangerous to return a new class instead of Big instance, users need check every input first.

if (foo !== undefined) {
   Big(foo)
}

of course, we still need to be careful to not pass undefined, but we can throw on Big(undefined), that's much easier to use and get noted.

To support creating new Big class, we can expose createBig() instead.

[MikeMcl]

It's too late, I think. That decision was made years ago.

It's unconventional but it's short and sweet and I'm okay with it.

Big.createBig() is okay but a bit of a mouthful in comparison. Big.create() was considered at the time also.

Anyway, using new Big() will throw an error, and even without new users would soon get an error when a method is called on what they think is an instance but is a constructor.

Thanks for the feedback.

[fisker]

Big.createBig() is okay but a bit of a mouthful in comparison.

I was thinking

import Big, {createBig} from 'big.js';

Big.create() sounds like shortcut for new Big()

users would soon get an error when a method is called on what they think is an instance but is a constructor.

Not always true, for example in this case,

function sum(array, initialValue) {
	return array.reduce((total, current) => total.plus(current), Big(initialValue))
}

console.log(sum([1,2,3], 0).toString()) // -> "6"
console.log(sum([], undefined).toString()) // -> The `Big` constructor 

[fisker]

In my project, I added a simple wrapper, to enforce new and prevent Big(undefined)

import Big from 'big.js';

class BigNumber {
	constrictor(value) {
		if (value === undefined) {
			throw new TypeError('...')
		}

		return new Big(value)
	}
}

export default BigNumber;

Didn't subclass since I'm not sure if it will work when I wrote it.

Just want to share how I use, and feel worth a try to propose a change to prevent such mistakes.

[fisker]

Maybe we can check arguments.length === 0 instead of compare n with undefined. I don't think anyone want a new constructor passes explicit undefined.

So the change will be almost unnoticeable.

[MikeMcl]

Sorry, I'm not seeing any compelling arguments.

Your wrapper seems a bit pointless when new Big() throws anyway. Might as well just use:

Big.create = n => new Big(n);

That way, you wouldn't have to create instances using new and you would also have your necessarily instance-creating create function.

I just noticed that big.js, decimal.js-light, decimal.js, and bignumber.js all have the same behavior.

Which behaviour? None of the others create a new constructor by calling the default constructor without new.

[fisker]

That way, you wouldn't have to create instances using new

That's exactly why I use class I want constructors be called with new, I don't like Big("1") either, but that's just a personal preference.

None of the others create a new constructor by calling the default constructor without new.

Really sorry, I read them too quick, I saw instanceof check and assumed they are the same code as here. My bad.