Add the input checkbox and its handler in the salesforce lightning component #inSalesforce

Add the input checkbox and its handler in the salesforce lightning component #inSalesforce

On your component page: 

<aura:component implements="flexipage:availableForAllPageTypes">

        <ui:inputCheckbox aura:id="demo" label="Sample" change="{!c.onCheck}"/>

</aura:component>

Client-side controller page:

({

    onCheck: function(cmp, event, helper){

        alert("!!!!!!!sample!!!!!!!");

        var checkboxCmp = cmp.find("demo");

        alert(checkboxCmp.get("v.value"));

    }

})

Visual: https://www.youtube.com/watch?v=P8u6gOR62sI