oc調用js就特別簡單了哨毁，只需WKWebView調用

• (void)evaluateJavaScript:completionHandler:方法即可。

/* @abstract Evaluates the given JavaScript string.
 @param javaScriptString The JavaScript string to evaluate.
 @param completionHandler A block to invoke when script evaluation completes or fails.
 @discussion The completionHandler is passed the result of the script evaluation or an error.
*/
- (void)evaluateJavaScript:(NSString *)javaScriptString completionHandler:(void (^ _Nullable)(_Nullable id, NSError * _Nullable error))completionHandler;

WKUserScript JS注入

在WebKit框架中，我們還可以預先添加JS方法竿裂，供其他人員調用许帐。WKUserScript就是幫助我們完成JS注入的類，它能幫助我們在頁面填充前或js填充完成后調用主经。核心方法荣暮。

/*! @abstract Returns an initialized user script that can be added to a @link WKUserContentController @/link.
 @param source The script source.
 @param injectionTime When the script should be injected.
 @param forMainFrameOnly Whether the script should be injected into all frames or just the main frame.
 */
- (instancetype)initWithSource:(NSString *)source injectionTime:(WKUserScriptInjectionTime)injectionTime forMainFrameOnly:(BOOL)forMainFrameOnly;

#pragma mark - get方法
- (WKWebView *)webView {
    if (_webView == nil) {
        // js配置
        WKUserContentController *userContentController = [[WKUserContentController alloc] init];
        [userContentController addScriptMessageHandler:self name:@"jsCallOC"];
        // js注入，注入一個alert方法罩驻，頁面加載完畢彈出一個對話框穗酥。
        NSString *javaScriptSource = @"alert(\"WKUserScript注入js\");";
        WKUserScript *userScript = [[WKUserScript alloc] initWithSource:javaScriptSource injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES];// forMainFrameOnly:NO(全局窗口)，yes（只限主窗口）
        [userContentController addUserScript:userScript];

        // WKWebView的配置
        WKWebViewConfiguration *configuration = [[WKWebViewConfiguration alloc] init];
        configuration.userContentController = userContentController;

        // 顯示W(wǎng)KWebView
        _webView = [[WKWebView alloc] initWithFrame:self.view.frame configuration:configuration];
        [self.view addSubview:_webView];
    }
    return _webView;
}

同時實現(xiàn)代理WKUIDelegate的方法：

#pragma mark alert彈出框
- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(void))completionHandler {
    NSLog(@"%s",__FUNCTION__);
    // 確定按鈕
    UIAlertAction *alertAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        completionHandler();
    }];
    // alert彈出框
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:message message:nil preferredStyle:UIAlertControllerStyleAlert];
    [alertController addAction:alertAction];
    [self presentViewController:alertController animated:YES completion:nil];
}