Prevent knockout validation from evaluating on initial load

Question

I have a simple view-model with a few required attributes... I want each input to highlight red if the corresponding property is not valid, but I don't want this highlighting to display when the page is initially loaded... only when a value changes or when the user tries to save / continue...

Right now it's validating the view-model on initial load because I'm specifying data-bind="css: { error: name.isValid() == false }", but I don't know of any other way to get this to work dynamically (similar to how jQuery unobtrusive validation works)...

var foo = { name: ko.observable().extend({required: true}) };

<div data-bind="css: { error: !name.isValid() }">
    <input type="text" data-bind="value: name" />
</div>

Any ideas on how to make this work would be appreciated... Thanks!

Answer 1

A better approach is to configure knockout validation to decorate the element with the validationElement class. This is done by adding this configuration option:

ko.validation.configure({ decorateElement: true });

Click here to see a jsfiddle demonstrating this.

****EDIT, IN RESPONSE TO COMMENT FROM QUESTION ASKER***

If you need to decorate the parent element, a more elegant and reusable solution is to apply this custom binding to the parent element.

Javascript

ko.bindingHandlers.parentvalElement = {
    update: function(element, valueAccessor, allBindingsAccessor, viewModel, bindingContext) {
        var valueIsValid = valueAccessor().isValid();
        if(!valueIsValid && viewModel.isAnyMessageShown()) {
            $(element).addClass("parentError");
        }
        else {
            $(element).removeClass("parentError");
        }
    }
};

And apply the binding in your HTML like so:

<form data-bind='submit:OnSubmit'>
    <label data-bind='parentvalElement:name'>
        <span>Name</span>
        <input data-bind="value: name" />
    </label>
    <input type='submit' value='submit' />
<form>

Take a look at this updated jsfiddle to see it in action.

Answer 2

So, here is the solution I came up with:

var Foo = function()
{
    this.name = ko.observable().extend({required: true}).isModified(false);
    this.validate: function()
    {
        if (!this.isValid())
        {
            //... loop through all validated properties and set .isModified(true)
            return false;
        }
        return true;
    };
    ko.validation.group(foo);
};

var Bar = function()
{
   this.foo = new Foo();
   this.errors = ko.observableArray([]); //<-- displays errors for entire page
   this.save = function()
   {
       if (!this.foo.validate())
       {
          this.errors(ko.toJS(this.foo.errors()));
       }
   };
}

ko.applyBindings(new Bar());

---

And here is the markup...

<div data-bind="with: foo">
    <div class="control-group"
         data-bind="css: { error: name.isModified() && !name.isValid() }">
        <label class="control-label">Name<span class="help-inline">*</span></label>
        <div class="controls">
            <input type="text" class="input-block-level" placeholder="Name"
                   data-bind="value: name, event: { blur: function () { name.isModified(true); }}" />
        </div>
    </div>

    <div class="alert alert-error"
         data-bind="visible: $parent.errors().length > 0">
        <h5>Errors!</h5>
        <ul data-bind="foreach: $parent.errors()">
            <li data-bind="text: $data"></li>
        </ul>
    </div>
</div>

<button type="submit" class="btn btn-primary" data-bind="click: save">Save</button>

---

and here is the CSS

.error { color: Red; font-weight: bold; }
.help-inline { display: none; }
.error .help-inline { display: inline-block; }
.error input { border-color: Red; }