form

tinywasm/form

Fast form generation from Go structs for TinyGo + WASM. Uses tinywasm/fmt exclusively (no standard library).

Quick Start

type User struct {
    Name  string `placeholder:"Full Name"`
    Email string
    Role  string `options:"admin:Admin,user:User"`
}

f, err := form.New("parent-id", &User{Name: "John"})
html := f.RenderHTML()    // render to HTML string

Public API

form.New(parentID string, structPtr any) (*Form, error)

Creates a Form from a struct pointer.

• Reflects exported fields → matches each to a registered Input by name/alias
• Copies struct field values into inputs
• Returns error if any exported field has no matching input
• Form id = parentID + "." + lowercase(structName)
• Default action = /lowercase(structName), method = POST

form.RegisterInput(inputs ...input.Input)

Registers custom input types globally. Called with ("", "") as dummy init args.

form.SetGlobalClass(classes ...string)

Sets CSS classes applied to all <form> elements.

(*Form) Methods

Render Modes

Struct Tags

type User struct {
    Name     string `placeholder:"Full Name" title:"Enter your full name"`
    Role     string `options:"admin:Admin,user:User"`
    Internal string `validate:"false"`
}

Field Matching

New() matches each exported struct field to a registered Input:

1. lowercase(FieldName) vs Input's htmlName or aliases
2. lowercase(StructName.FieldName) vs Input's aliases

Matching is case-insensitive. First match wins.

Input Interface

type Input interface {
    dom.Component  // GetID(), SetID(), RenderHTML(), Children()
    HTMLName() string                  // HTML type ("text", "email", etc.)
    FieldName() string                 // struct field name
    ValidateField(value string) error  // field validation
    Clone(parentID, name string) Input // creates new instance
}

WASM Event Flow

dom.Mount("root", myForm)
  → myForm.RenderHTML() injected into DOM
  → myForm.OnMount() called
      → one "input"/"change" listener at <form> level
          → finds input by event.target.id
          → calls SetValues(val) + ValidateField(val)
      → one "submit" listener
          → PreventDefault()
          → SyncValues() → Validate() → OnSubmit callback

Documentation Index

• SKILL.md — LLM compact reference (start here)
• Input Types & Base API
• API Reference
• Design & Architecture
• Struct Tags