regex digits one or more code example

Example 1: regex match number

For matching an integer number of one single char/digit, specify:
[0-9]
But for matching any number of more than one char/digit; add "+":
[0-9]+
Example for matching hour with minutes of HH:MM format in a file:
grep "[0-9]\+\:[0-9]\+" file.txt

Example 2: javascript regex Zero or one occurrence

// javascript regex Zero or one occurrence
let neighbor = /neighbou?r/;
console.log(neighbor.test("neighbour")); // true
console.log(neighbor.test("neighbor")); // true