Hello again,
I just made it. It works with no errors but can anyone check my code is correct? Thanks 
<!-- Custom sidebar widget -->
<script type="text/discourse-plugin" version="0.8">
const ajax = require('discourse/lib/ajax').ajax;
if(api.getCurrentUser() != null) {
let currentUser = Discourse.User.currentProp('username');
api.registerConnectorClass('discovery-below', 'sidebar', {
setupComponent(args, component) {
ajax("/u/" + currentUser + "/summary.json").then (function(result){
stinkinBadges = [];
userLikesReceived = result.user_summary.likes_received;
userLikesGiven = result.user_summary.likes_given;
result.badges.forEach(function(badges){
stinkinBadges.push(badges);
});
component.set('userLikesReceived', userLikesReceived);
component.set('userLikesGiven', userLikesGiven);
component.set('stinkinBadges', stinkinBadges);
component.set('userName', api.getCurrentUser().name);
component.set('user', api.getCurrentUser().username);
});
}
})};
</script>