more cleanup

internal/runtime/runtime.go

@@ -94,11 +94,14 @@ func (r *Runtime) transformCode(tsCode string) ([]byte, error) {
 	})
 
 	if len(result.Errors) > 0 {
-		var allErrs []string
-		for _, e := range result.Errors {
-			allErrs = append(allErrs, e.Text)
+		var b strings.Builder
+		for i, e := range result.Errors {
+			if i > 0 {
+				b.WriteString(", ")
+			}
+			b.WriteString(e.Text)
 		}
-		return nil, fmt.Errorf("transpilation failed: %s", strings.Join(allErrs, ", "))
+		return nil, fmt.Errorf("transpilation failed: %s", b.String())
 	}
 
 	return result.Code, nil
@@ -112,7 +115,7 @@ func callFunc(this *qjs.This, fn functions.Function) (*qjs.Value, error) {
 	for i := range min(len(fnArgs), len(qjsArgs)) {
 		rVal, err := qjs.JsArgToGo(qjsArgs[i], fnArgs[i])
 		if err != nil {
-			panic(err)
+			return nil, fmt.Errorf("argument conversion failed: %w", err)
 		}
 		allArgs = append(allArgs, rVal.Interface())
 	}