GoogleAuthComponent.cmp

<aura:component controller="GoogleAuthService" implements="lightning:isUrlAddressable,force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" access="global" >
  	<aura:handler name="init" value="{!this}" action="{!c.doInit}" />
    <aura:attribute name="accessToken" type="String" />
    <lightning:card title="Google Transcription">
    	<lightning:button variant="brand" label="Authorize Google" title="Google Drive Auth" onclick="{! c.doAuth }" />
   	</lightning:card>
</aura:component>

GoogleAuthComponentController.js

({
    doInit : function(component, event, helper) {
        if(component.get("v.pageReference") != undefined && component.get("v.pageReference") != 'undefined') {
            var code = component.get("v.pageReference").state.code;
            
            var url = window.location.href;
            console.log('url',url);
            
            function getParameterByName(name, url) {
                if (!url) url = window.location.href;
                name = name.replace(/[\[\]]/g, '\\$&');
                var regex = new RegExp('[?&]' + name + '(=([^&#]*)|&|#|$)'),
                                         results = regex.exec(url);
                                         console.log('===results==',results);
                                         if (!results) return null;
                                         if (!results[2]) return '';
                return decodeURIComponent(results[2].replace(/\+/g, ' '));
            }
            var code = getParameterByName('code');
            if(code != undefined) {
                var action = component.get('c.getAccessToken');
                action.setParams({
                    'code' : code
                });
                action.setCallback(this, function(response){
                    var status = response.getState();
                    if(status === "SUCCESS"){
                        var accessToken = response.getReturnValue();
                        component.set("v.accessToken", accessToken);
                    }
                });
                
                $A.enqueueAction(action);
            }
        }
    },
    
    doAuth : function(component, event, helper) {
        
        var action  = component.get("c.createAuthURL");
        action.setCallback(this, function(response){
            var status = response.getState();
            if(status === "SUCCESS"){
                var authUrl = response.getReturnValue();
                window.location.href = response.getReturnValue();
            }
        });
        
        $A.enqueueAction(action);
    }
})