注意以下枚举

/*! @enum WKUserScriptInjectionTime
 @abstract when a user script should be injected into a webpage.
 @constant WKUserScriptInjectionTimeAtDocumentStart    Inject the script after the document element has been created, but before any other content has been loaded.
 @constant WKUserScriptInjectionTimeAtDocumentEnd      Inject the script after the document has finished loading, but before any subresources may have finished loading.
 */
NS_ASSUME_NONNULL_BEGIN

typedef NS_ENUM(NSInteger, WKUserScriptInjectionTime) {
    WKUserScriptInjectionTimeAtDocumentStart,
    WKUserScriptInjectionTimeAtDocumentEnd
} API_AVAILABLE(macos(10.10), ios(8.0));

修改js系统方法实现（alert为例）

• 例1：
  • js代码

          <input type="button" value="重定义系统方法" onclick="locationClick()" />
          function locationClick() {
               alert('4444')
           }
  

  • OC代码注入

   // 以下两种注入方式都可以
   NSString *jsCode = @"alert = (function (oriAlertFunc){ \
                         return function(task)\
                         {\
                          window.webkit.messageHandlers.ocZRAction.postMessage(task);\
                           oriAlertFunc.call(alert,task);\
                         }\
                         })(alert);";
   NSString *jsCode3 = @"alert =  function(task)\
      {\
       window.webkit.messageHandlers.asyncAction.postMessage(task);\
      }";
   [self.webView.configuration.userContentController addUserScript:[[WKUserScript alloc] initWithSource:jsCode injectionTime:WKUserScriptInjectionTimeAtDocumentStart forMainFrameOnly:YES]];
  
  

注入JS未实现方法（alert为例）

• 例1、
  • JS代码

          <input type="button" value="注入JS未实现方法" onclick="shareClick()" />
  

  • OC代码注入 注意：这里使用WKUserScriptInjectionTimeAtDocumentEnd或injectionTime:WKUserScriptInjectionTimeAtDocumentStart都可以

      NSString *jsCode6 = @"shareClick =  function(task)\
             {\
              window.webkit.messageHandlers.GoBack.postMessage(task);\
             }";
    [self.webView.configuration.userContentController addUserScript:[[WKUserScript alloc] initWithSource:jsCode6 injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES]];
    [self.webView.configuration.userContentController addUserScript:[[WKUserScript alloc] initWithSource:jsCode6 injectionTime:WKUserScriptInjectionTimeAtDocumentStart forMainFrameOnly:YES]];
  

修改JS方法的原有实现

• 例1、
  • JS代码

       <input type="button" value="重定义JS方法实现" onclick="colorClick()" />
      function colorClick() {
                alert('55555')
           }
  

  • OC代码
    注意：这里使用WKUserScriptInjectionTimeAtDocumentEnd不能用WKUserScriptInjectionTimeAtDocumentStart

    NSString *jsCode7 = @"colorClick =  function(task)\
                {\
                 window.webkit.messageHandlers.GoBack.postMessage(task);\
                }";
     [self.webView.configuration.userContentController addUserScript:[[WKUserScript alloc] initWithSource:jsCode7 injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES]];