Call Javascript Function From Native Code In Wkwebview

JavaScript is an essential part of modern web development, enabling dynamic and interactive features on websites and web applications. When working with a WKWebView in an iOS app, you may encounter scenarios where you need to call a JavaScript function from your native Objective-C or Swift code. In this article, we'll walk you through the steps to achieve this seamless communication between JavaScript and native code.

To call a JavaScript function from native code in a WKWebView, you can use the WKWebView's evaluateJavaScript method. This method allows you to execute a JavaScript snippet within the context of the web view and retrieve the result, if needed. Here's how you can make use of this powerful feature in your iOS app development:

1. **Accessing WKWebView Instance**: First, you need to ensure that you have a reference to the WKWebView instance in your native code. If you've already set up the WKWebView in your app, you can access it by its property. Ensure that the WKWebView has loaded the content where the JavaScript function resides.

2. **Calling JavaScript Function**: Once you have access to the WKWebView instance, you can call the evaluateJavaScript method on it. This method takes two parameters: a JavaScript snippet to be executed and a completion handler that can optionally return the result of the JavaScript execution.

3. **Example Code**:

// Objective-C
[self.webView evaluateJavaScript:@"yourJavaScriptFunction()" completionHandler:^(id _Nullable result, NSError * _Nullable error) {
    if (error == nil) {
        NSLog(@"JavaScript function executed successfully");
        // Handle the result if needed
    } else {
        NSLog(@"Error executing JavaScript function: %@", error.localizedDescription);
    }
}];

// Swift
webView.evaluateJavaScript("yourJavaScriptFunction()") { (result, error) in
    if let error = error {
        print("Error executing JavaScript function: (error.localizedDescription)")
    } else {
        print("JavaScript function executed successfully")
        // Handle the result if needed
    }
}

4. **Handling Results**: The result parameter in the completion handler contains the outcome of the JavaScript function execution. You can process this result in your native code as needed. Remember to handle errors that may occur during the JavaScript execution.

5. **Security Considerations**: When invoking JavaScript from native code, be cautious of injection attacks or unintended side effects. Always validate any input data passed between JavaScript and native code to prevent security vulnerabilities.

In conclusion, being able to call JavaScript functions from native code in a WKWebView opens up a wide array of possibilities for enhancing the interactivity and functionality of your iOS apps. By leveraging the evaluateJavaScript method and handling the results effectively, you can seamlessly bridge the gap between your native app and web content. Stay curious, keep exploring, and happy coding!