node_modules/ajv-formats/node_modules/ajv/lib/vocabularies/jtd/nullable.ts

import type {KeywordCxt} from "../../compile/validate"
import {_, not, nil, Code, Name} from "../../compile/codegen"

export function checkNullable(
  {gen, data, parentSchema}: KeywordCxt,
  cond: Code = nil
): [Name, Code] {
  const valid = gen.name("valid")
  if (parentSchema.nullable) {
    gen.let(valid, _`${data} === null`)
    cond = not(valid)
  } else {
    gen.let(valid, false)
  }
  return [valid, cond]
}

export function checkNullableObject(cxt: KeywordCxt, cond: Code): [Name, Code] {
  const [valid, cond_] = checkNullable(cxt, cond)
  return [valid, _`${cond_} && typeof ${cxt.data} == "object" && !Array.isArray(${cxt.data})`]
}