validation failed but still saves the record

Question

The validation for email alerts me but when I click Ok it saves the record to salesforce

Here is the code:

<apex:page controller="myAudit">
  <script type="text/javascript">
     function validate() { 
            var ex= document.getElementsByClassName('email')[0].value;
            var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/i;
            var a = re.test(email);
                  alert("re.text_" + a);
            if (a == true)
             { alert('Valid email address'); }
            else { alert('Invalid email address'); }                  
        }        

    </script>   
    <apex:form id="audit">
        <apex:pageblock >
          <apex:pageblockSection columns="1">
            <p><apex:inputText value="{!account}" label="Account"/></p>
            <apex:inputText id="Survey" value="{!txtSurvey}" label="SurveyName"/>
            <apex:inputText id="email" value="{!email}" Label="Email" styleClass="examNote"/>
              <apex:commandButton action="{!save}" onclick="validate();" value="save"/>
          </apex:pageblockSection>

        </apex:pageblock>
    </apex:form>
</apex:page>

Answer 1

Modify your javascript function like below:

if (a == true)
             { alert('Valid email address'); 
return true;
}
            else { alert('Invalid email address');
return false:
 }                  
        } 

Also modifing command button. Add return validate()

<apex:commandButton action="{!save}" onclick="return validate();" value="save"/>

Hope it helps!