Example of Characters Constraint Regex

regex.js

// Check string contains only one space
const pattern = new RegExp(/^\S+(?: \S+)*$/);

// Check if string is url
const pattern = new RegExp('^(https?:\\/\\/)?'+ // protocol
    '((([a-z\\d]([a-z\\d-]*[a-z\\d])*)\\.)+[a-z]{2,}|'+ // domain name
    '((\\d{1,3}\\.){3}\\d{1,3}))'+ // OR ip (v4) address
    '(\\:\\d+)?(\\/[-a-z\\d%_.~+]*)*'+ // port and path
    '(\\?[;&a-z\\d%_.~+=-]*)?'+ // query string
    '(\\#[-a-z\\d_]*)?$','i');
    
// Check if space is the only non-numeric-alphabet character
const pattern = new RegExp(/^$|.*\S+.*/);

// Check if string contains space
const pattern = new RegeExp(/^\S*$/);

// Check if string only has alphabet, dot and ' characters
const pattern = new RegeExp(/^[a-zA-Z .']+$/);

// Check if string only has numeric characters
const pattern = new RegeExp(/^\d+$/);