用于小写字母开头的驼峰格式的REGEX模式

Question

I need to write a validation in javascript that will detect the input value is in camelcase format. The first letter expected to be lowercase.

I got some code from stackflow and made it in JSFIDDLE.

Its working for both helloWorld and HelloWorld

I would appreciate if someone could help me to complete the task..

function myFunction() {
var str = "HeLloWorld";
var patt = new RegExp("[a-z]([a-z0-9]*[a-z][a-z0-9]*[A-Z]|[a-z0-9]*[A-Z][A-Z0-9]*[a-z])[A-Za-z0-9]*");
var res = patt.test(str);
document.getElementById("demo").innerHTML = res;
}

Note: I have been playing around with it. So it will not be the correct regex.

Answer 1

I have not delved too deep into the pattern, but it seems working for your input only when you add the boundaries or anchors. The problem with matching HelloWorld is that your pattern matched elloWorld and RegExp#test() returned true.

^[a-z]([a-z0-9]*[a-z][a-z0-9]*[A-Z]|[a-z0-9]*[A-Z][A-Z0-9]*[a-z])[A-Za-z0-9]*$‌​

Or

\b[a-z]([a-z0-9]*[a-z][a-z0-9]*[A-Z]|[a-z0-9]*[A-Z][A-Z0-9]*[a-z])[A-Za-z0-9]*\b

See the regex demo

 function myFunction() { var str = "HelloWorld"; var patt = /\\b[az]([a-z0-9]*[az][a-z0-9]*[AZ]|[a-z0-9]*[AZ][A-Z0-9]*[az])[A-Za-z0-9]*\\b/; var res = patt.test(str); document.getElementById("demo").innerHTML = "HelloWorld match with word boundaries: " + res + "<br/>"; var patt2 = /^[az]([a-z0-9]*[az][a-z0-9]*[AZ]|[a-z0-9]*[AZ][A-Z0-9]*[az])[A-Za-z0-9]*$/; document.getElementById("demo").innerHTML += "HelloWorld match with start/end string anchors: " + patt2.test(str); } 

 <p>The test() method returns true if it finds a match, otherwise it returns false.</p> <p>Click the button to search a string for the character "e".</p> <button onclick="myFunction()">Try it</button> <p id="demo"></p>