Generator

Base class for all generators.

Here we will use the integer generator as an example:

const { integer } = require("chance-generators")

API

map(mapper)

Returns a new generator where all values generated from the original will be mapped with the given mapper function.

expect(
  integer({ min: 0, max: 100 })
    .map(v => `${v} kr`)
    .take(3),
  "to equal",
  ["37 kr", "80 kr", "96 kr"]
);

All generators in the mapped value will be unwrapped:

const ranges = integer({ min: 0, max: 100 }).map(to => ({
  from: integer({ min: 0, max: to }),
  to
}));
 
expect(ranges.take(5), "to equal", [
  { from: 30, to: 37 },
  { from: 17, to: 96 },
  { from: 57, to: 73 },
  { from: 36, to: 60 },
  { from: 7, to: 15 }
]);

first([options])

Calls values and returns the first item:

expect(integer.first(), "to equal", -2260084377780223);

Any options will be forwarded to the values method:

expect(integer.first({ seed: 666 }), "to equal", 3610754225799169);

Notice, don't use this method to generate multiple values, you should either use values to get an iterator and call next on that, or use the take method seen below. This is only for cases where you just need one value generated.

take(n, [options])

Calls values and takes the n first items from the iterator:

expect(integer.take(3), "to equal", [-2260084377780223, 5342043492581377, 8119347222413313]);

Any options will be forwarded to the values method:

expect(integer.take(3, { seed: 666 }), "to equal", [
  3610754225799169,
  -7158602909351935,
  6200315372109825
]);

values([options])

Returns an iterator for the generator with a default seed:

const iterator = integer.values();
 
expect([iterator.next(), iterator.next(), iterator.next()], "to equal", [
  -2260084377780223,
  5342043492581377,
  8119347222413313
]);

You can optionally also provide a seed for the random generator:

const seededIterator = integer.values({ seed: 666 });
 
expect([seededIterator.next(), seededIterator.next(), seededIterator.next()], "to equal", [
  3610754225799169,
  -7158602909351935,
  6200315372109825
]);

It is also possible to make the generated values completely random by using a random seed:

const randomIterator = integer.values({ seed: null });
 
expect(
  [randomIterator.next(), randomIterator.next(), randomIterator.next()],
  "to have items satisfying",
  "to be a number"
);