regex to check number code example

Example 1: just number regex

// https://regex101.com/r/qyq3PG/1
// or 
/^[0-9]*$/

Example 2: 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 3: number pattern js

/^[\+\-]?\d*\.?\d+(?:[Ee][\+\-]?\d+)?$/

/* 
	matched values:
    -2.14e10
    +14E-20
    42.69
*/