Try out these example digits to get valid results and any US telephone numbers that you've got. For invalid results just input values that don't match the formats below.
- 1 555-555-5555
- 1 (555)555-5555
- 1(555)555-5555
- 1 555 555 5555
- 5555555555
- 555-555-5555
- (555)555-5555
- 1 (555) 555-5555
- 1 456 789 4444
Found this tool that helped me in coming up with the regular expressions used and also here is an awesome guide on how to go about with the project.