How to build a welcome webpart to show the current user name after welcome in sharepoint online
closed as unclear what you're asking by Gaurravs, Mohamed El-Qassas MVP♦ Oct 25 '18 at 7:36
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
To build a welcome webpart, microsfot has a very well documented steps given here.
Here in step 7, they have declared some default properties to show on webpart. like description, test, etc.
Similarly, you can create one more property to show the display name of current user.
To get the details of current logged in user, check this question.
Also, in SharePoint online you can get the display name of current user using following code:
var currentUserName = _spPageContextInfo.userDisplayName;