How to create OnClick button on visualforce page in Salesforce?

Hi Deepak,

You can take help from this below example of vf page to create an onclick event on vf page:-

<apex:page standardController="Lead" extensions="D_B_LeadCntrlr">
<apex:includeScript value="/soap/ajax/29.0/connection.js"/>
<apex:includeScript value="/soap/ajax/29.0/apex.js"/>
<script >

    var success = 'false';
    function myFunction(){
        var Retrieve_DB_Detail = '{!Retrieve_DB_Details}';
        if(Retrieve_DB_Detail == false || Retrieve_DB_Detail == 'false'){
            alert('You cannot perform DB Check with retrieve DB details as false');
        }else{
            var result = sforce.apex.execute("RetriveDBDetailsController","getDBDetails",{leadId:"{!leadId}"});
            alert(result);
             window.location.reload();
        }
    }

    function showSuccess(){
        if(showSuccess == 'true'){
            alert(success);
           window.location.reload();
        }
    }
    </script>
<apex:form >

    <apex:actionFunction name="callMethod" action="{!callMethod}" onComplete="showSuccess()"/>

        <apex:PageBlock >
            <div align="center" draggable="false" >
                <apex:CommandButton value="D&B Check" onclick="myFunction()" />
            </div>
        </apex:PageBlock>
    </apex:form>    
</apex:page>