Find sys_id of user record when only data available is a string field with user_name

[Lon Landry4]

For use case reasons a string field is required to capture user data.

I need to find sys_id of user record when only data available is a string field with user_name.

I was hoping to accomplish this task as simply as possible, so a Script Includes/Client script is not the direction I want to go in...

I am trying the below script in workflow but the query result is "undefined".

var rqstdFor = current.variables.someUser;
var userGR = new GlideRecord('sys_user');
userGR.addQuery('user_name',rqstdFor);
userGR.query();
var testThis = userGR.query();
gs.addInfoMessage(testThis);

[Lon Landry4]

This got me going in the right direction, I still needed to add gr.getValue('sys_id').

But in error I was trying gr.getValue.sys_id