Kudos to Samantha Ming for her thoughts on printing ranges natively on JavaScript.
This looked really promising and cool. So I though about implementing within a custom class and without generators so it can run without regenerator-runtime in Nodejs.
This is what I came up with and it doesn't have any side effects mentioned by the original article.
The purpose of the class is to create a number that can be spread into an array reaching to 0 from either positive or negative side.
Since the implementation basically uses Symbol.iterator
it also works for looping with for ...of.
This is what the code looks like.
/**
* An experimental iterable number class
*
* It implements Symbol.iterator, so one can use it with for-of loop and spread.
*
* This is just an experiment, I don't know why someone would actually use it,
* but if you are and need some sort of license, here you go.
*
* copyright 2018 Swashata Ghosh <swashata@wpquark.com>
* This code is licensed under MIT license
*/
class IterableNumber {
constructor(num = 0) {
if (Number.isNaN(Number.parseInt(num, 10)) || !Number.isFinite(num)) {
throw new Error('Must pass a valid finite integer');
}
this.num = num;
this[Symbol.iterator] = () => ({
next: this.generateNext(this.num),
});
}
generateNext = top => {
// increase the number by one, if positive, else decrease by one
let running = top > 0 ? top + 1 : top - 1;
return () => {
// If the running number is zero, then it was done
// in the previous step
if (running === 0) {
return {
done: true,
};
}
// Otherwise, let's decrease or increase the number, based on
// positivity
running = this.num > 0 ? running - 1 : running + 1;
return {
value: running,
done: false,
};
};
};
}Now we can use it like this.
const spreadedNum = [...new IterableNumber(9)];
console.log(spreadedNum); // [ 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 ]
for (const i of new IterableNumber(20)) {
console.log(i); // 20, 19, 18, ... 1, 0
}
const spreadedNumN = [...new IterableNumber(-9)];
console.log(spreadedNumN); // [ -9, -8, -7, -6, ..., -2, -1, 0 ]
const spreadedZ = [...new IterableNumber(0)];
console.log(spreadedZ); // [ 0 ]
try {
const invalidSpread = [...new IterableNumber('duh?')];
console.log(invalidSpread);
} catch (e) {
console.log(e); // [Error: Must pass a valid finite integer]
}If you have any questions, shoot.