Overriding the placement of validation error messages in knockout-validation

By default, knockout-validation places error messages just after the input element containing the error. This may not be what you want, and you can create UI elements of your own and bind them to validation error messages but this means writing a lot of boilerplate markup and it messes up the HTML. An alternative to this is to override the knockout-validation function that creates the error messages on the page. For example:

ko.validation.insertValidationMessage = function(element) {
    var span = document.createElement('SPAN');
    span.className = "myErrorClass";

    if ($(element).hasClass("error-before"))
        element.parentNode.insertBefore(span, element);
    else
        element.parentNode.insertBefore(span, element.nextSibling);

    return span;
};  

In this example I check whether the input element contains the custom class “error-before”, and if so, I move the error message to before rather than after the input field.

Another example, suitable for Bootstrap when using input groups:

ko.validation.insertValidationMessage = function(element) {
    var span = document.createElement('SPAN');
    span.className = "myErrorClass";

    var inputGroups = $(element).closest(".input-group");
    if (inputGroups.length > 0) {
        // We're in an input-group so we place the message after
        // the group rather than inside it in order to not break the design
        $(span).insertAfter(inputGroups);
    } else {
        // The default in knockout-validation
        element.parentNode.insertBefore(span, element.nextSibling);
    }
    return span;
};

One disadvantage of this is that we have no access to the knockout-validation options such as “errorMessageClass” so we have to hard code that value here (“myErrorClass” in the examples above.

/Emil

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