Question

I need to add some validation that will only allow one capital letter in a string that may include spaces. The capital letter can be anywhere in the string, but can only be used once or not at all.

I was going to incorporate the solution below as a separate rule, but I have this bit of validation and wondering if I can just tweak it to get the desired result:

// Validate Sentence Case
if(dataEntryCaseId.toString().match("4")){
    var newValue = toTitleCase(value);
    if(newValue != value){
        for(var x = 1, j = value.length; x < j; x++){
            if(value.charAt(x) != newValue.charAt(x)){
                valid = false;
                $("#text_10").attr({"value":$("#text_10").attr("value").replace(value.charAt(x), "")});
                finalVal = finalVal.replace(value.charAt(x), "");
            }
        }
    }
}


if(!valid){
    for(var x = 0, j = styleNoteJsonData.styleGroupNote.length; x < j; x++){
        if(styleNoteJsonData.styleGroupNote[x].styleName == styleGroupName){
            alert(styleNoteJsonData.styleGroupNote[x].styleNote);           
            $(".styleNote").addClass("alertRed");
            SendErrorMessage(styleNoteJsonData.styleGroupNote[x].styleNote);                
        }
    }

Answer 1

"this is A way to do it with regex".match(/^[^A-Z]*[A-Z]?[^A-Z]*$/)

Regex breaks down like this…

start of string (^) followed by not capital letter ([^A-Z]) zero or more times (*) follow by optional (?) capital letter ([A-Z]) followed by not capital letter ([^A-Z]) zero or more times (*) followed by end of string ($)

---

EDIT: simpler method based on idea from @IAbstractDownvoteFactory’s answer

var string = "This is a simple way to do it"

// match all capital letters and store in array x
var x = string.match(/[A-Z]/g)

// if x is null, or has length less than 2 then string is valid
if(!x || x.length < 2){
    // valid
} else {
    // not valid
}

Regex matches all capital letters, and returns an array of matches. The length of the array is how many capitals there are, so less than 2 returns true.