allow returning values from use_eval

packages/web/src/util.rs

@@ -1,6 +1,10 @@
 //! Utilities specific to websys
 
+use std::str::FromStr;
+
 use dioxus_core::*;
+use serde::de::Error;
+use serde_json::Value;
 
 /// Get a closure that executes any JavaScript in the webpage.
 ///
@@ -15,12 +19,24 @@ use dioxus_core::*;
 ///
 /// The closure will panic if the provided script is not valid JavaScript code
 /// or if it returns an uncaught error.
-pub fn use_eval<S: std::string::ToString>(cx: &ScopeState) -> &dyn Fn(S) {
+pub fn use_eval<S: std::string::ToString>(
+    cx: &ScopeState,
+) -> &dyn Fn(S) -> Result<Value, serde_json::Error> {
     cx.use_hook(|| {
         |script: S| {
-            js_sys::Function::new_no_args(&script.to_string())
-                .call0(&wasm_bindgen::JsValue::NULL)
-                .expect("failed to eval script");
+            let body = script.to_string();
+            if let Ok(value) =
+                js_sys::Function::new_no_args(&body).call0(&wasm_bindgen::JsValue::NULL)
+            {
+                if let Ok(stringified) = js_sys::JSON::stringify(&value) {
+                    let string: String = stringified.into();
+                    Value::from_str(&string)
+                } else {
+                    Err(serde_json::Error::custom("Failed to stringify result"))
+                }
+            } else {
+                Err(serde_json::Error::custom("Failed to execute script"))
+            }
         }
     })
 }