Helper to keep calling a function until a criterion is met

[matthewmayer]

Clear and concise description of the problem

We often get requests for additional options for methods to further restrict the output in some way, e.g. limiting the length or the range of outputs, or excluding certain types of data

• Add Min/Max length for faker.name.fullName and faker.name.lastName #1203
• Lorem EN word.ts contains a single character in the pool #3261
• Add option to exclude emoji #2623

Suggested solution

In some cases, rather than add many more options, it may make sense to just repeatedly generate until a certain criterion is met. This could be wrapped in a helpers function.

pseudocode.

/** repeatedly calls a function until a condition is met and returns the result */
function generateUntil(func, condition) {
    let result = null
    do {
        result = func()
    } while (!condition(result))
    return result
}

Usage:

const shortCompanyName = faker.helpers.generateUntil(faker.company.name, (name) => name.length < 30)
const femaleNameStartingWithJ = faker.helpers.generateUntil(()=>faker.person.firstName("female"), (name) => name.startsWith("J"))

Alternative

Write the loop manually

Additional context

Note if you provide an impossible condition, this gives an infinite loop. Might need a automatic failure after a certain number of loops.

[github-actions]

Thank you for your feature proposal.

We marked it as "waiting for user interest" for now to gather some feedback from our community:

• If you would like to see this feature be implemented, please react to the description with an up-vote (:+1:).
• If you have a suggestion or want to point out some special cases that need to be considered, please leave a comment, so we are aware about them.

We would also like to hear about other community members' use cases for the feature to give us a better understanding of their potential implicit or explicit requirements.

We will start the implementation based on:

• the number of votes (:+1:) and comments
• the relevance for the ecosystem
• availability of alternatives and workarounds
• and the complexity of the requested feature

We do this because:

• There are plenty of languages/countries out there and we would like to ensure that every method can cover all or almost all of them.
• Every feature we add to faker has "costs" associated to it:
  • initial costs: design, implementation, reviews, documentation
  • running costs: awareness of the feature itself, more complex module structure, increased bundle size, more work during refactors

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