public void hasJavascriptMethod(String handlerName, final WVJBMethodExistCallback callback) {
        callHandler("_hasJavascriptMethod", handlerName, new WVJBResponseCallback() {
            @Override
            public void onResult(Object data) {
                callback.onResult((boolean) data);
            }
        });
    }
Test whether the handler exist in javascript

@param handlerName
@param callback
app/src/main/java/com/example/jingbin/webviewstudy/view/WVJBWebView.java