Android window.ReactNativeWebView.postMessage issue

@Titozzz I didn’t realize that the targetOrigin argument must be omitted in window.ReactNativeWebView.postMessage().

If the targetOrigin(*) is added, it will throw the method does not exist error!

// This one won't work.
window.ReactNativeWebView.postMessage(JSON.stringify(data), "*");

// This will work.
window.ReactNativeWebView.postMessage(JSON.stringify(data));

I just had the same error and narrowed it down in my case to a javascript binding issue. You can easily reproduce the java bridge method can't be invoked on a non injected object error by assigning the window.ReactNativeWebView.postMessage to a local variable then trying to invoke that:

let postMessageProxy = window.ReactNativeWebView.postMessage;
postMessageProxy('hey....') //boom :(

By assigning to a local variable and calling that, javascript is changing the functions this and the Android WebView appears to be quite unhappy with that. It is quite easy to work around by ensuring the binding is preserved:

let postMessageProxy = function(data) { window.ReactNativeWebView.postMessage(data); }
postMessageProxy('hey....') //yay :)

As a real world example and the reason I came across this was for some code which was shared between hosting in a WebView or an iframe and I was trying to do this:

//find a postMessage to talk to hoster
let postMessage = window.parent.postMessage;
if(window.ReactNativeWebView) {
    postMessage = window.ReactNativeWebView.postMessage;
}

postMessage('hey');