How to Execute JavaScript on Android

Execute javascript without webview in Android

UPDATE 2018: AndroidJSCore has been superseded by LiquidCore, which is based on V8. Not only does it include the V8 engine, but all of Node.js is available as well.

You can execute JavaScript without a WebView. You can use AndroidJSCore. Here is a quick example how you might do it:

HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet("http://your_website_here/file.js");
HttpResponse response = client.execute(request);
String js = EntityUtils.toString(response.getEntity());

JSContext context = new JSContext();
context.evaluateScript(js);
context.evaluateScript("question.vote(0);");

However, this most likely won't work outside of a WebView, because I presume you are not only relying on JavaScript, but AJAX, which is not part of pure JavaScript. It requires a browser implementation.

Is there a reason you don't use a hidden WebView and simply inject your code?

// Create a WebView and load a page that includes your JS file
webView.evaluateJavascript("question.vote(0);", null);

Run JavaScript in Android webview

Well I replaced:

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
    webview.evaluateJavascript(javascript, null);
} else {
    webview.loadUrl("javascript:(function(){" + javascript + "})()");
}

with

webview.setWebViewClient(new WebViewClient() {
    public void onPageFinished(WebView webview, String url) {
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
            webview.evaluateJavascript(javascript, null);
        } else {
            webview.loadUrl("javascript:(function(){" + javascript + "})()");
        }
    }
});

and it just WORKS!

How to call javascript from Android?

There is a hack:

Bind some Java object so that it can be called from Javascript with WebView:
```
addJavascriptInterface(javaObjectCallback, "JavaCallback")
```

Force execute javascript within an existing page by

WebView.loadUrl("javascript: var result = window.YourJSLibrary.callSomeFunction();
    window.JavaCallback.returnResult(result)");

(in this case your java class JavaObjectCallback should have a method returnResult(..))

Note: this is a security risk - any JS code in this web page could access/call your binded Java object. Best to pass some one-time cookies to loadUrl() and pass them back your Java object to check that it's your code making the call.

Calling JavaScript from Android

According to CW answer,

You need to wait until your page is loaded

private void helloJs(){
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
        webView.evaluateJavascript("javascript:hello();", null);
    } else {
        webView.loadUrl("javascript:hello();");
    }
}

webView.setWebViewClient(new WebViewClient() {
    public void onPageFinished(WebView view, String url) {
        helloJs();
    }
});

unable to execute javascript code in Android WebView from Service

What kind of data you want to pass to Javascript? You could use the WebView.addJavascriptInterface() to "Plant" methods on the HTML document so you can call them from Javascript, invoke in native and return data back to Javascript. Will that help?

Running JavaScript Console in Android Chrome (without pc)

Oh I got it.

Open your browser and go to "Add bookmarks".
Paste this code as URL:

javascript:(function () { var script = document.createElement('script'); script.src="//cdn.jsdelivr.net/npm/eruda"; document.body.appendChild(script); script.onload = function () { eruda.init() } })();

Now open a site and go in search bar. You will end up with this. Image here
Press the bookmark that you have recently created and will seen a floating button press on that and boom!

Run javascript code in Webview

From kitkat onwards use evaluateJavascript method instead loadUrl to call the javascript functions like below

    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.KITKAT) {
        webView.evaluateJavascript("var FunctionOne = function () {"
            + "  try{document.getElementsByClassName('test')[0].style.color='red';}catch(e){}"
            + "};", null);
    } else {
        webView.loadUrl("javascript:"
            + "var FunctionOne = function () {"
            + "  try{document.getElementsByClassName('test')[0].style.color='red';}catch(e){}"
            + "};");
    }

Enable Javascript for your webview by adding the following line

wb.getSettings().setJavaScriptEnabled(true);