Sample Code:

Component:

1. <aura:component implements=“force:appHostable” >  
2.       
3.     <aura:attribute name=“strText” type=“String”/>  
4.       
5.    <div class=“slds-box slds-theme_default”>  
6.   
7.        <span onkeypress=“{!c.callKeyUp}”>  
8.              
9.            <lightning:input label=“Enter Text”  
10.                             value=“{!v.strText}” />  
11.              
12.        </span>  
13.           
14.     </div>  
15.       
16. </aura:component>  

Component Controller:

1. ({  
2.   
3.     callKeyUp : function(component, event, helper) {  
4.           
5.         if ( event.keyCode == 13 )  
6.             alert(component.get(“v.strText”));  
7.           
8.     }  
9.       
10. })  

Output:


Enter some text and click Enter button.