<\/p>\n
Updated August 2026 \u2014 full tutorial restored for this URL.<\/em><\/p>\n This regular expressions<\/strong> tutorial is a practical cheat sheet: metacharacters, groups, and examples you can paste into JavaScript or Python.<\/p>\n 1. Literals and character classes<\/strong><\/p>\n 2. Quantifiers and anchors<\/strong><\/p>\n 3. Groups and alternation<\/strong><\/p>\n 4. Common recipes<\/strong><\/p>\n 5. Test in JS and Python<\/strong><\/p>\n Always write unit tests for regex used in validation \u2014 one wrong Updated August 2026 \u2014 full tutorial restored for this URL. This regular expressions tutorial is a practical cheat sheet: metacharacters, groups, and examples you can … <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"pagelayer_contact_templates":[],"_pagelayer_content":"","footnotes":""},"categories":[35],"tags":[],"class_list":["post-2294","post","type-post","status-publish","format-standard","hentry","category-algorithms"],"acf":[],"_links":{"self":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts\/2294","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/comments?post=2294"}],"version-history":[{"count":3,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts\/2294\/revisions"}],"predecessor-version":[{"id":2461,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts\/2294\/revisions\/2461"}],"wp:attachment":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/media?parent=2294"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/categories?post=2294"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/tags?post=2294"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\n
\n
.<\/code> any char (except newline unless flag)<\/li>\n\\d<\/code> digit, \\w<\/code> word, \\s<\/code> whitespace<\/li>\n[abc]<\/code> one of, [^abc]<\/code> none of, [a-z]<\/code> range<\/li>\n<\/ul>\n\n
*<\/code> 0+, +<\/code> 1+, ?<\/code> 0 or 1, {2,5}<\/code> range<\/li>\n^<\/code> start, $<\/code> end, \\b<\/code> word boundary<\/li>\n*?<\/code> \/ +?<\/code> when matching HTML-ish snippets<\/li>\n<\/ul>\n(\\d{3})-(\\d{2}) # capturing groups\n(?:https?) # non-capturing\ncat|dog # alternation\n<\/code><\/pre>\n^[^\\s@]+@[^\\s@]+\\.[^\\s@]+$ # simple email (demo only)\n^\\+?[0-9\\-\\s]{7,15}$ # rough phone\nhttps?:\/\/[^\\s]+ # URLs in text\n<\/code><\/pre>\n\/\/ JavaScript\nconst re = \/^\\d{4}-\\d{2}-\\d{2}$\/;\nconsole.log(re.test(\"2026-08-26\"));\n\n# Python\nimport re\nprint(bool(re.fullmatch(r\"\\d{4}-\\d{2}-\\d{2}\", \"2026-08-26\")))\n<\/code><\/pre>\n.<\/code> can open security holes.<\/p>\n","protected":false},"excerpt":{"rendered":"