Does a Number Exist?

Create a function which validates whether a given number exists, and could represent a real life quantity. Inputs will be given as a string.

Examples

validStrNumber("3.2") ➞ true

validStrNumber("324") ➞ true

validStrNumber("54..4") ➞ false

validStrNumber("number") ➞ false

Notes

Accept numbers such as .5 and 0003.