I can see the panic of small business owners spreading across Facebook:
New tax law! No deductions for mileage, business expenses, travel, conferences!
I can't survive without these deductions!
I'll have to close my business!
The Senate and House versions for tax reform still need to be reconciled before the law can go to the President for signature, but this much seems clear: most of the gutting of old law affects individuals on Form 1040 pages 1 & 2, and Schedule A.
If you are a business owner filing Schedule C, a landlord filing Schedule E, a farmer filing Schedule F, or an owner of a "pass-through" such as a S-corp, LLC, or partnership, the deductions your business can claim have not vanished under the new law. The old rule stands: expenses that are ordinary and necessary in the conduct of your business are deductible as business expenses.
Exception: it looks like your entertainment expenses (hockey tickets, hunting lodge, theater, etc), which are only 50% deductible under current law (2017 and prior years), will likely become nondeductible under proposed law. Business meals, in general, will remain 50% deductible.