Conditionals

if / then / else


const schema = new SchemaBuilder()
  .object()
  .properties({
    type: (s) => s.string(),
    username: (s) => s.string(),
    apiKey: (s) => s.string(),
  })
  .if((s) => s.object().properties({ type: (s) => s.const("user") }))
  .then((s) => s.object().required(["username"]))
  .else((s) => s.object().required(["apiKey"]))
  .build();
// type === "user" → must have username; otherwise → must have apiKey

elseIf — multiple conditions

The elseIf extension chains conditions without deep nesting.


const accountSchema = new SchemaBuilder()
  .object()
  .properties({
    accountType: (s) => s.string(),
    username: (s) => s.string(),
    email: (s) => s.string(),
    companyName: (s) => s.string(),
    taxId: (s) => s.string(),
  })
  .required(["accountType"])
  .if((s) => s.object().properties({ accountType: (s) => s.const("personal") }))
  .then((s) => s.object().required(["username", "email"]))
  .elseIf((s) =>
    s.object().properties({ accountType: (s) => s.const("business") }),
  )
  .then((s) => s.object().required(["companyName", "taxId", "email"]))
  .elseIf((s) =>
    s.object().properties({ accountType: (s) => s.const("enterprise") }),
  )
  .then((s) => s.object().required(["companyName", "taxId"]))
  .else((s) => s.object().required(["email"]))
  .build();

This generates { if, then, elseIf: [{ if, then }, ...], else }, which Jet-Validator handles during compilation.

Without elseIf you’d nest each condition inside the previous else — a deep, hard-to-read chain. elseIf flattens it.


// Standard approach - deeply nested
.if(...)
  .then(...)
  .else(s => s
    .if(...)
      .then(...)
      .else(s => s
        .if(...)
          .then(...)
        .else(...)
      )
  )
// Nested hell!

Nested conditionals


const advancedRulesSchema = new SchemaBuilder()
  .object()
  .properties({
    country: (s) => s.string(),
    state: (s) => s.string(),
    zipCode: (s) => s.string(),
    postalCode: (s) => s.string(),
  })
  .if((s) => s.object().properties({ country: (s) => s.const("US") }))
  .then((s) =>
    s
      .object()
      .required(["state", "zipCode"])
      .if((s) => s.object().properties({ state: (s) => s.const("California") }))
      .then((s) =>
        s.object().properties({
          zipCode: (s) => s.string().pattern("^9[0-6]\\d{3}$"),
        }),
      )
      .end(), // only and always call .end() if you don't need else
  )
  .elseIf((s) => s.object().properties({ country: (s) => s.const("UK") }))
  .then((s) => s.object().required(["postalCode"]))
  .end()
  .build();

If you don’t end a conditional with .else(), always call .end() to close it.