telephone number validator javascript
// Valid US Phone Number but can be tweaked. const telephoneCheck = str => { const regExp = /^1?\s?(\(\d{3}\)|\d{3})(\s|-)?\d{3}(\s|-)?\d{4}$/gm return regExp.test(str) } telephoneCheck("27576227382"); /* Regular Expression Explanation Below !!! */ /* Expression : /^1?\s?(\(\d{3}\)|\d{3})(\s|-)?\d{3}(\s|-)?\d{4}$/gm ^ asserts position at start of a line 1? matches the character 1 literally (case sensitive) ? Quantifier — Matches between zero and one times, as many times as possible, giving back as needed (greedy) \s? matches any whitespace character (equal to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]) ? Quantifier — Matches between zero and one times, as many times as possible, giving back as needed (greedy) 1st Capturing Group (\(\d{3}\)|\d{3}) 1st Alternative \(\d{3}\) \( matches the character ( literally (case sensitive) \d{3} matches a digit (equal to [0-9]) {3} Quantifier — Matches exactly 3 times \) matches the character ) literally (case sensitive) 2nd Alternative \d{3} \d{3} matches a digit (equal to [0-9]) {3} Quantifier — Matches exactly 3 times 2nd Capturing Group (\s|-)? ? Quantifier — Matches between zero and one times, as many times as possible, giving back as needed (greedy) 1st Alternative \s \s matches any whitespace character (equal to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]) 2nd Alternative - - matches the character - literally (case sensitive) \d{3} matches a digit (equal to [0-9]) {3} Quantifier — Matches exactly 3 times 3rd Capturing Group (\s|-)? ? Quantifier — Matches between zero and one times, as many times as possible, giving back as needed (greedy) 1st Alternative \s \s matches any whitespace character (equal to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]) 2nd Alternative - \d{4} matches a digit (equal to [0-9]) {4} Quantifier — Matches exactly 4 times $ asserts position at the end of a line Global pattern flags g modifier: global. All matches (don't return after first match) m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string) */ // With love @kouqhar