How does Yup’s casting system work?

Yup’s Schema.cast() method lets you attempt to coerce an input to match a specific schema. For example, you might use the number() type to coerce a value like "5" to 5.

Failed casts usually return null, but can also return values like NaN or unexpected strings.

// Attempts to coerce values to the correct type
const parsedUser = userSchema.cast({
  name: 'jimmy',
  age: '24',
  createdOn: '2014-09-23T19:25:25Z',
})
// ✅  { name: 'jimmy', age: 24, createdOn: Date }

If you know that your input is already parsed, you can use { strict: true } to skip the casting:

// ❌  ValidationError "age is not a number"
const parsedUser = await userSchema.validate(
  {
    name: 'jimmy',
    age: '24',
  },
  { strict: true },
)