add initial version

package.json

@@ -0,0 +1,11 @@
+{
+	"name": "@conduitry/svelte-tiny-validation",
+	"version": "0.0.0",
+	"description": "A tiny unframework for form validation in Svelte.",
+	"private": true,
+	"homepage": "https://git.chor.date/Conduitry/svelte-tiny-validation",
+	"type": "module",
+	"exports": {
+		".": "./validation.js"
+	}
+}

validation.js

@@ -0,0 +1,59 @@
+import { get, writable } from 'svelte/store';
+
+export const field = (validator) => {
+	let node = null;
+	let value;
+	let message_enabled = false;
+	const validity = { valid: true, message: null };
+
+	const { set, subscribe } = writable(validity);
+
+	const update = () => {
+		const message = node && validator(value);
+		validity.valid = !message;
+		validity.message = message_enabled ? message : null;
+		set(validity);
+	};
+
+	const enable_message = () => {
+		message_enabled = true;
+		update();
+	};
+
+	const action = (new_node, new_value) => {
+		node = new_node;
+		value = new_value;
+		update();
+
+		node.addEventListener('blur', enable_message);
+
+		return {
+			update(new_value) {
+				value = new_value;
+				update();
+			},
+			destroy() {
+				node.removeEventListener('blur', enable_message);
+				node = null;
+				message_enabled = false;
+				update();
+			},
+		};
+
+	};
+
+	action.validate = () => node && enable_message();
+
+	action.subscribe = subscribe;
+
+	return action;
+};
+
+export const validate = (...fields) => {
+	let valid = true;
+	for (const field of fields) {
+		field.validate();
+		valid = valid && get(field).valid;
+	}
+	return valid;
+};