Lightning Component for Stopwatch

SK_StopWatch.cmp

<aura:component >
    <aura:handler name="init" value="{! this }" action="{!c.doInit}"/>
    <aura:attribute name="ltngCurrTime" type="String" default="00:00:00"/>
    <aura:attribute name="ltngIsDisplayed" type="boolean" default="false"/> 
    
    <div class="slds-card slds-align_absolute-center" style="width:250px;padding:8px;" >
        <div class="slds-grid slds-wrap" >
            <div class="slds-col slds-size_1-of-1 slds-align_absolute-center" >
                <b>Stopwatch</b>
            </div>
            <div class="slds-col slds-size_1-of-1 slds-align_absolute-center" >
                {!v.ltngCurrTime}
            </div>
            <div class="slds-col slds-size_1-of-1 slds-align_absolute-center">
                <lightning:button variant="brand" label="Start" onclick="{! c.handleStartClick }" disabled="{!v.ltngIsDisplayed}"/>
                <lightning:button variant="brand" label="Stop" onclick="{! c.handleStopClick }" disabled="{! !v.ltngIsDisplayed}"/>
                <lightning:button variant="brand" label="Reset" onclick="{! c.handleResetClick }" />
            </div>
        </div>
    </div>    
</aura:component>

SK_StopWatchApp.app

<aura:application extends="force:slds">
	  <c:SK_StopWatch />
</aura:application>

SK_StopWatchController.js

({
    doInit : function(component, event, helper) {
		console.log("diinit get called!!");
	},
    handleStartClick : function(component, event, helper) {
		console.log("start button clicked!!");
        helper.setStartTimeOnUI(component);
	},
    handleStopClick : function(component, event, helper) {
		console.log("stop button clicked!!");
        helper.setStopTimeOnUI(component);
	},
    handleResetClick : function(component, event, helper) {
		console.log("Reset button clicked!!");
        helper.setResetTimeOnUI(component);
	}   
})

SK_StopWatchHelper.js

({
    waitingTimeId: null,
	setStartTimeOnUI : function(component) {
        component.set("v.ltngIsDisplayed",true);
        var currTime =component.get("v.ltngCurrTime");
        var ss = currTime.split(":");
        var dt = new Date();
        dt.setHours(ss[0]);
        dt.setMinutes(ss[1]);
        dt.setSeconds(ss[2]);
        
        var dt2 = new Date(dt.valueOf() + 1000);
        var temp = dt2.toTimeString().split(" ");
        var ts = temp[0].split(":");
        
        component.set("v.ltngCurrTime",ts[0] + ":" + ts[1] + ":" + ts[2]);
        this.waitingTimeId =setTimeout($A.getCallback(() => this.setStartTimeOnUI(component)), 1000);
    },
    setStopTimeOnUI : function(component) {
        component.set("v.ltngIsDisplayed",false);
        window.clearTimeout(this.waitingTimeId);
    },
    setResetTimeOnUI : function(component) {
        component.set("v.ltngIsDisplayed",false);
        component.set("v.ltngCurrTime","00:00:00");
        window.clearTimeout(this.waitingTimeId);
    }
})