javascript: Remove illegal characters in url

Recently I needed to create valid urls for pages using javascript. Also this time I thought it must be some out-of-the-box code for that in SharePoint. The first thing I came up  was the “Add page” dialog.  I found that the actual dialog was in the _layouts virtual folder:

/_layouts/15/CreatePublishingPageDialog.aspx

Bingo, it does the validation in the client side. This is the responsible javascript function that resides directly in the page:

function UpdateUrl() {
  LoadTermContextInfo();
  var hiddenPageUrlLabelExtensionClientId = "<%=hiddenPageUrlLabelExtension.ClientID%>";
  var hiddenPageUrlLabelExtension = document.getElementById(hiddenPageUrlLabelExtensionClientId);
  var pageNamePreviewUrlLabelClientId = "<%=pageNamePreviewUrlLabel.ClientID%>";
  var pageNamePreviewUrlLabel = document.getElementById(pageNamePreviewUrlLabelClientId);
  if( pageNamePreviewUrlLabel != null ) {
    var nameInputTextBoxClientId = "<%=nameInput.ClientID%>";
    var nameInputTextBox = document.getElementById(nameInputTextBoxClientId);
    var allowSpaces = false;
    if( GetInnerText(hiddenPageUrlLabelExtension) != "" ) {
      var suggestUrlValue = "";
      for (var i=0; i < nameInputTextBox.value.length; i++) {
         var currentChar = nameInputTextBox.value.charAt(i);
         if (IndexOfIllegalCharInUrlLeafName(currentChar) == -1 
			&& !(currentChar == ' ' && allowSpaces == false) 
			&& currentChar != '.' && currentChar != '+') {
           suggestUrlValue += currentChar;
         }
         else if (currentChar == ' ' 
			|| currentChar == '+' 
			|| (currentChar == '.' && i > 0 && i < (nameInputTextBox.value.length - 1))) {
          suggestUrlValue += '-';
        }
      }
      UpdatePreviewUrl( suggestUrlValue );
    } else {
      if( g_timerId != 0 ) {
        window.clearTimeout(g_timerId);
      }
      g_timerId = window.setTimeout(OnFriendlyUrlNameChanged, 500);
    }
  }
}

This function iterates through all the characters in the page url and removes the illegal characters. The space, plus sign and the dot become a hyphen. To determine if a character is illegal, it relies on another javascript function called: IndexOfIllegalCharInUrlLeafName. This function can be found in the init.js or init.debug.js:

function IndexOfIllegalCharInUrlLeafName(strLeafName) {
    for (var i = 0; i < strLeafName.length; i++) {
        var ch = strLeafName.charCodeAt(i);

        if (strLeafName.charAt(i) == '.' && (i == 0 || i == strLeafName.length - 1))
            return i;
        if (ch < 160 && (strLeafName.charAt(i) == '/' || !LegalUrlChars[ch]))
            return i;
    }
    return -1;
}

This function checks a char against an array of all characters: LegalUrlChars from the same file: init.js.

To use this UpdateUrl function, we have to remove the references to the fields from the Add Page Dialog. Of course, we won’t overwrite this original function, we don’t want to break the SharePoint OOB functionality. Here is how my new function looks like:

var takana = {};
function takana.updateUrl(url) {
  var allowSpaces = false;
  if( url )
  {
    var suggestUrlValue = "";
    var length = url.length;
    for (var i=0; i < length; i++)     {
       var currentChar = url.charAt(i);
       if (IndexOfIllegalCharInUrlLeafName(currentChar) == -1
            && !(currentChar == ' ' && allowSpaces == false)
            && currentChar != '.' && currentChar != '+') {
         suggestUrlValue += currentChar;
       }
       else if (currentChar == ' '
            || currentChar == '+'
            || (currentChar == '.'
                     && i > 0
                   && i < (nameInputTextBox.value.length - 1))) {
         suggestUrlValue += '-';
      }
    }
  }
}

Server Side

For those of you who want run this operation on the server, here is the code written in C#:

//" # % & * : < > ? \ / { } ~ |
var illegalChars = @"[""#%&\*:\<\>\?\\\/\{\}~\|]";

pageName = Regex.Replace(pageName, illegalChars, string.Empty);

var punctuation = @"[\s\.;\+]";
pageName = Regex.Replace(pageName, punctuation, "-");

//remove "--"
pageName = Regex.Replace(pageName, @"\-{2,}", "-");

pageName = string.Format("{0}.aspx", pageName);

//do it like the built-in dialog, lower case
pageName = pageName.ToLower();

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