Get URL parameters in Lightning Components

 You can get lightning parameter in two way : 

1)  

lightning:isUrlAddressable Interface : Get URL parameters in Lightning Components

We can fetch URL param by using "{!v.PageReference.state.parameterName}" where parameterName is URL parameter name.

<aura:component  implements="lightning:isUrlAddressable,force:appHostable" access="global">

    <aura:attribute name="urlParam" type="string"/>

    <div class="slds-card">

    If you implements "lightning:isUrlAddressable" interface, then by 

        using v.pageReference,you can get URL params.

    <div class="slds-box">  

        Account Name is :  <b>{!v.pageReference.state.accname}</b>

        </div>

    </div> 

</aura:component>

"/lightning/n/tabName?accname=Naresh Thakur"

Output is : 

Account Name is : Naresh Thakur

2) You can write code in js component 

For Ex 

doInit : function(component, event, helper) {       

         var sPageURL = decodeURIComponent(window.location.search.substring(1));

         var sURLVariables = sPageURL.split('&');

         var sParameterName;

         for (var i = 0; i < sURLVariables.length; i++) {

             sParameterName = sURLVariables[i].split('=');             

             if (sParameterName[0] === 'conId') {

                 component.set('v.tempConId',sParameterName[1]);

             }

         }

         

        // Other code goes here

    },

Call it 

https://YourURL/Pagename?conId = aio000000000ADSuiq