Added golines playground

cmds/golines/main.go

@@ -0,0 +1,40 @@
+//go:build js && wasm
+
+package main
+
+import "syscall/js"
+
+func main() {
+	document := js.Global().Get("document")
+	element := func(id string) js.Value { return document.Call("getElementById", id) }
+	source, width := element("source"), element("max-len")
+	output, message := element("output"), element("message")
+	render := func() {
+		maxLen := width.Get("valueAsNumber").Int()
+		element("width-value").Set("textContent", maxLen)
+		tabLen := 4
+		if maxLen < 80 {
+			tabLen = 2
+		}
+		element("tab-value").Set("textContent", tabLen)
+		source.Get("style").Set("tabSize", tabLen)
+		output.Get("style").Set("tabSize", tabLen)
+		formatted, err := formatSource(source.Get("value").String(), maxLen)
+		if err != nil {
+			output.Set("value", "")
+			message.Set("textContent", err.Error())
+			source.Call("setAttribute", "aria-invalid", "true")
+			return
+		}
+		source.Call("removeAttribute", "aria-invalid")
+		output.Set("value", string(formatted))
+		message.Set("textContent", "")
+	}
+	listener := js.FuncOf(func(this js.Value, args []js.Value) any { render(); return nil })
+	source.Call("addEventListener", "input", listener)
+	width.Call("addEventListener", "input", listener)
+	source.Set("disabled", false)
+	width.Set("disabled", false)
+	render()
+	select {}
+}