Question

我被告知此代码警告字符串，但不返回。我很抱歉，完全是初学者......我不确定自己做错了什么，我跑的每一项测试都说它很好。感谢

function myFavFood() {
}   

var food;

if (food == "pizza") {
  alert("I love Pizza");
} 
else if (food == "Hot pockets") {
  alert("hot pockets woo");
}
else {
  alert("I have bad taste in foods");
}

Answer 1

这是你想要的吗？

org.hsqldb.HsqlException: data exception: string data, right truncation
at org.hsqldb.error.Error.error(Unknown Source)
at org.hsqldb.error.Error.error(Unknown Source)
at org.hsqldb.types.CharacterType.convertToTypeLimits(Unknown Source)
at org.hsqldb.Table.enforceTypeLimits(Unknown Source)
at org.hsqldb.Table.insertSingleRow(Unknown Source)
at org.hsqldb.StatementDML.insertRowSet(Unknown Source)
at org.hsqldb.StatementInsert.getResult(Unknown Source)
at org.hsqldb.StatementDMQL.execute(Unknown Source)
at org.hsqldb.Session.executeCompiledStatement(Unknown Source)
at org.hsqldb.Session.execute(Unknown Source)
at org.hsqldb.jdbc.JDBCPreparedStatement.fetchResult(Unknown Source)
at org.hsqldb.jdbc.JDBCPreparedStatement.executeUpdate(Unknown Source)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:208)
at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:96)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:58)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3032)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3558)
at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:98)
at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:492)
at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:197)
at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:181)
at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:216)
at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:334)
at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:289)
at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:126)
at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:84)
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206)
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149)
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75)
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1181)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:344)
at com.sun.proxy.$Proxy58.persist(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:291)
at com.sun.proxy.$Proxy58.persist(Unknown Source)
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:433)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:436)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:421)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:393)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.data.repository.core.support.RepositoryFactorySupport$DefaultMethodInvokingMethodInterceptor.invoke(RepositoryFactorySupport.java:506)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodIntercceptor.invoke(CrudMethodMetadataPostProcessor.java:122)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at com.sun.proxy.$Proxy60.save(Unknown Source)
at com.andirod.controller.EventController.saveEvents(EventController.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)

Answer 2

非常简单，真的：要返回它而不是alert(something)，你需要简单输入return aVariable;

e.g。

function myFavFoodReturn(food) {

var response;

 if (food == "pizza") {
  response = "I love Pizza";
 } 
else if (food == "Hot pockets") {
  response = "hot pockets woo";
 }
 else {
  response = "I have bad taste in foods";
 } 
  return response; //this returns but doesn't alert. 
}

在这里播放警报与回归：https://jsbin.com/mufuba/2/edit?js,console

===

区别在于如何处理变量。

警告变量只是在屏幕上显示它，而返回它不会在屏幕上显示它。您可以将它视为在物理上发送信件（返回信件）和简单地向某人显示信件而不是将信件发送给他们（提醒它）之间的区别。以下是差异的快速演示：

var someVariable = "this is an awesome variable";

function alertSomething() {
  alert(someVariable);
}

function returnSomething(){
  return someVariable;
}


var a = alertSomething();

var b = returnSomething();

//this will output '"the alert method doesn't return a value: undefined"':
console.log("the alert method doesn't return a value, see: " + a);

//this will output '"but the return method does: this is an awesome variable"'
console.log("but the return method does: " + b);

JSBIN工作演示：https://jsbin.com/ruvaxi/1/edit?js,console

请注意，通常一个return语句会停止执行某个函数，因此它需要是您希望在函数中执行的最后一件事。 e.g。

function myFunction(a) {
   return a*2; //this line returns the 'a' argument, but doubled
   alert('awesomesauce');  //this line will never run, because of the return.
}

Answer 3

首先，永远不会调用函数myFavFood，因此永远不会执行它。但是，这部分代码：

var response;

 if (food == "pizza") {
  response = "I love Pizza";
 } 
else if (food == "Hot pockets") {
  response = "hot pockets woo";
 }
 else {
  response = "I have bad taste in foods";
 } 
  return response; //this returns but doesn't alert. 
}

执行没有问题只是因为它不是函数的一部分（你需要将代码放在{}中），代码的那部分是“全局的”并在浏览器打开你的页面时执行。

如果你想调用该函数并执行代码 INSIDE HER ，你需要这样做：

    function myFavFood() {
                var food;

                if (food == "pizza") {
                  alert("I love Pizza");
                } 
                else if (food == "Hot pockets") {
                  alert("hot pockets woo");
                }
                else {
                  alert("I have bad taste in foods");
                } 
            }
**myFavFood()**

（请注意，代码现在位于{}键内，如果您想调用并执行代码，则需要输入“functionNameAnd（）”。

对于最后一部分，如果你想要返回一些只是输入return的东西，你想要返回到函数之外的变量或元素：

像这样：

function myFavFood() {
            var food;

            if (food == "pizza") {
              alert("I love Pizza");
              return food;
            } 
            else if (food == "Hot pockets") {
              alert("hot pockets woo");
              return food;
            }
            else {
              alert("I have bad taste in foods");
            } 
        }

现在，如果使用变量调用该函数，该变量将获取返回元素的值。

所以，如果你这样做：

var something = myFavFood（），食物变量是披萨，函数将返回“披萨”，变量将具有值披萨。

我警告字符串，但没有返回

3 个答案: