yup
Validate data with Yup schemas. Use when adding form validation, defining API request schemas, validating configuration, or building type-safe validation pipelines in JavaScript/TypeScript.
Best use case
yup is best used when you need a repeatable AI agent workflow instead of a one-off prompt.
Validate data with Yup schemas. Use when adding form validation, defining API request schemas, validating configuration, or building type-safe validation pipelines in JavaScript/TypeScript.
Teams using yup should expect a more consistent output, faster repeated execution, less prompt rewriting.
When to use this skill
- You want a reusable workflow that can be run more than once with consistent structure.
When not to use this skill
- You only need a quick one-off answer and do not need a reusable workflow.
- You cannot install or maintain the underlying files, dependencies, or repository context.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/yup/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How yup Compares
| Feature / Agent | yup | Standard Approach |
|---|---|---|
| Platform Support | Not specified | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | Unknown | N/A |
Frequently Asked Questions
What does this skill do?
Validate data with Yup schemas. Use when adding form validation, defining API request schemas, validating configuration, or building type-safe validation pipelines in JavaScript/TypeScript.
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
SKILL.md Source
# Yup
## Overview
Yup is a schema validation library for JavaScript. Define schemas declaratively, validate data, and get detailed error messages. Works with Formik, react-hook-form, and standalone. TypeScript-first with type inference.
## Instructions
### Step 1: Schemas
```typescript
import * as yup from 'yup'
const userSchema = yup.object({
name: yup.string().min(2).max(100).required(),
email: yup.string().email().required(),
age: yup.number().positive().integer().min(13).max(120),
role: yup.string().oneOf(['admin', 'member', 'viewer']).default('member'),
tags: yup.array().of(yup.string()).min(1).max(10),
address: yup.object({
street: yup.string().required(),
city: yup.string().required(),
zip: yup.string().matches(/^\d{5}$/, 'Must be 5 digits'),
}),
})
// Validate
const user = await userSchema.validate(data, { abortEarly: false })
// Type inference
type User = yup.InferType<typeof userSchema>
```
### Step 2: Custom Validation
```typescript
const passwordSchema = yup.string()
.min(8)
.matches(/[A-Z]/, 'Must contain uppercase')
.matches(/[0-9]/, 'Must contain number')
.matches(/[^A-Za-z0-9]/, 'Must contain special character')
const signupSchema = yup.object({
password: passwordSchema.required(),
confirmPassword: yup.string()
.oneOf([yup.ref('password')], 'Passwords must match')
.required(),
})
```
### Step 3: Conditional Validation
```typescript
const schema = yup.object({
contactMethod: yup.string().oneOf(['email', 'phone']).required(),
email: yup.string().when('contactMethod', {
is: 'email',
then: (s) => s.email().required('Email required when contact method is email'),
}),
phone: yup.string().when('contactMethod', {
is: 'phone',
then: (s) => s.matches(/^\+\d{10,15}$/).required('Phone required'),
}),
})
```
## Guidelines
- `abortEarly: false` returns all errors at once — better UX than one-at-a-time.
- Use `InferType` to derive TypeScript types from schemas — single source of truth.
- For new projects, consider Zod instead — better TypeScript inference and ecosystem.
- Yup is still the standard for Formik integration.
- `.when()` for conditional validation — fields required only in certain contexts.Related Skills
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