{"id":609,"date":"2018-03-11T20:39:34","date_gmt":"2018-03-11T18:39:34","guid":{"rendered":"https:\/\/html-online.com\/articles\/?p=609"},"modified":"2023-12-20T13:57:02","modified_gmt":"2023-12-20T11:57:02","slug":"random-string-pattern-generator-javascript","status":"publish","type":"post","link":"https:\/\/html-online.com\/articles\/random-string-pattern-generator-javascript\/","title":{"rendered":"Random string pattern generator in JavaScript"},"content":{"rendered":"

In this article I’m going to present a JavaScript code that generates a random string in a certain pattern. The JS function<\/a> takes a string that matches the given pattern and returns a random string that contains the same type of characters in the same order as the sample.<\/strong>
\n\"random
\n<\/p>\n

Example<\/h2>\n

Input<\/strong>: AA aaa1111 ### Aaaaaa
\n<\/em>Interpreted as<\/strong>: Two capital letters, one space, three lowercase letters, four numbers, three special characters and a capitalized six-letter word.
\nExample result that matches the pattern: <\/strong>XC tmr4990 %&@ Yvhwfd<\/em><\/p>\n

I could have specified AB abc1234 !@# Abcdef<\/em> for the input or any other string that matches the desired result.<\/p>\n

The JavaScript Code<\/h2>\n

The function below distinguishes lower and capital letters, numbers and handles everything else as special characters but you can tweak the code to match your needs.<\/p>\n

function randomStringPattern<\/span>(input) {\n  var text =<\/span> \"\"<\/span>;\n  var possible;\n  for<\/span> (var j =<\/span> 0<\/span>; j <<\/span> input.length<\/span>; j++<\/span>) {\n    if<\/span> (input[j] ==<\/span> \" \"<\/span>) {\n        possible =<\/span> ' '<\/span>;\n    } else<\/span> if<\/span> ((input[j] ==<\/span> input[j].toUpperCase<\/span>()) &<\/span>&<\/span> (input[j] !<\/span>=<\/span> input[j].toLowerCase<\/span>())) {\n        possible =<\/span> \"ABCDEFGHIJKLMNOPQRSTUVWXYZ\"<\/span>;\n    } else<\/span> if<\/span> ((input[j] ==<\/span> input[j].toLowerCase<\/span>()) &<\/span>&<\/span> (input[j] !<\/span>=<\/span> input[j].toUpperCase<\/span>())) {\n        possible =<\/span> \"abcdefghijklmnopqrstuvwxyz\"<\/span>;\n    } else<\/span> if<\/span> ('0123456789'<\/span>.indexOf<\/span>(input[j]) !<\/span>==<\/span> -<\/span>1<\/span>) {\n        possible =<\/span> \"0123456789\"<\/span>;\n    } else<\/span> {\n        possible =<\/span> \"#!@~$%^&*)-_\"<\/span>\n    }\n    text +<\/span>=<\/span> possible.charAt<\/span>(Math<\/span>.floor<\/span>(Math<\/span>.random<\/span>() *<\/span> possible.length<\/span>));\n    }\n  return<\/span> text;\n}\n<\/pre>\n
Live Demo<\/h2>\n
The example below generates ten strings that match this pattern: AA aaa1111 ### Aaaaaa<\/strong>
\nSwitch to the Result tab to see the output:
\n