JavaScript synchronous native communication to WKWebView

Question

Is synchronous communication between JavaScript and Swift/Obj-C native code possible using the WKWebView?

These are the approaches I have tried and have failed.

Answer 1

I was facing a similar issue, i resolved it by storing promise callbacks.

The js that you load in your web view via WKUserContentController::addUserScript

var webClient = {
    id: 1,
    handlers: {},
};

webClient.onMessageReceive = (handle, error, data) => {
    if (error && webClient.handlers[handle].reject) {
        webClient.handlers[handle].reject(data);
    } else if (webClient.handlers[handle].resolve){
        webClient.handlers[handle].resolve(data);
    }

    delete webClient.handlers[handle];
};

webClient.sendMessage = (data) => {
    return new Promise((resolve, reject) => {
       const handle = 'm' + webClient.id++;
       webClient.handlers[handle] = { resolve, reject };
       window.webkit.messageHandlers..postMessage({data: data, id: handle});
   });
}

Perform Js Request like

webClient.sendMessage().then((response) => {
...
}).catch((reason) => {
...
});

Receive request in userContentController :didReceiveScriptMessage

Call evaluateJavaScript with webClient.onMessageReceive(handle, error, response_data).