How to know which button was pressed in lightning component?

How to know which button was pressed in lightning component?

To find out which button was pressed in a component containing multiple buttons, use Component.getLocalId().

Let’s look at a component that contains multiple buttons. Each button has a unique local ID, set by an aura:id attribute.

<!--c:buttonPressed-->
<aura:component >
    <aura:attribute name="whichButton" type="String" />
    
    <p>You clicked: {!v.whichButton}</p>

    <ui:button aura:id="button1" label="Click me" press="{!c.nameThatButton}"/>
    <ui:button aura:id="button2" label="Click me too" press="{!c.nameThatButton}"/>
</aura:component>

Use event.getSource() in the client-side controller to get the button component that was clicked. Call getLocalId() to get the aura:id of the clicked button.

/* buttonPressedController.js */
({
    nameThatButton : function(cmp, event, helper) {
        var whichOne = event.getSource().getLocalId();
        console.log(whichOne);
        cmp.set("v.whichButton", whichOne);
    }
})

Example Component: 

Controller.Js  : Highlighted code

out put:

for reference : 

https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/js_cb_which_button_pressed.htm