Valid Zip Code

Zip codes consist of 5 consecutive digits. Given a string, write a function to determine whether the input is a valid zip code. A valid zip code is as follows:

• Must only contain numbers (no non-digits allowed).
• Must not contain any spaces.
• Must not be greater than 5 digits in length.

Examples

isValid("59001") ➞ true

isValid("853a7") ➞ false

isValid("732 32") ➞ false

isValid("393939") ➞ false

Notes

N/A