Prevent a double click on a button with knockout.j

问题:

What is the best way to disable a button so a double click doesn't occur with knockout.js. I have some users doing some quick clicking causing multiple ajax requests. I assume knockout.js can handle this in several ways and wanted to see some of the alternatives out there.

回答1:

Use a semaphore (spinning lock). Basically, you count how many clicks an element has registered and if it is more than 1 you return false and don't allow the following clicks. A timeout function could be used to clear the lock so that they could click again after say, 5 seconds. You could modify the example from http://knockoutjs.com/documentation/click-binding.html

As seen here:

<div>
 You've clicked <span data-bind="text: numberOfClicks"></span> times
 <button data-bind="click: incrementClickCounter">Click me</button>
</div>

<script type="text/javascript">
 var viewModel = {
     numberOfClicks : ko.observable(0),
     incrementClickCounter : function() {
         var previousCount = this.numberOfClicks();
         this.numberOfClicks(previousCount + 1);
     }
 };
</script>

By changing the logic inside the nested function to

if( this.numberOfClicks() > 1 ){
 //TODO: Handle multiple clicks or simply return false
 // and perhaps implement a timeout which clears the lockout
}

回答2:

I ran into a similar problem with a form wizard submitting data via Ajax on button click. We have 4 buttons selectively visible for each step. We created a boolean observable ButtonLock and returned from the submission function if it was true. Then we also data-bound the disable of each button to the ButtonLock observable

ViewModel:

var viewModel = function(...) {
    self.ButtonLock = ko.observable(false);

    self.AdvanceStep = function (action) {
        self.ButtonLock(true);
        // Do stuff
        // Ajax call
    }

    self.AjaxCallback = function(data) {
        // Handle response, update UI
        self.ButtonLock(false);
    }

Button:

<input type="button" id="FormContinue" name="FormContinue" class="ActionButton ContinueButton"
    data-bind="
        if: CurrentStep().actions.continueAction,
        disable: ButtonLock,
        value: CurrentStep().actions.continueAction.buttonText,
        click: function() {
            AdvanceStep(CurrentStep().actions.continueAction);
        }"/>

If you just need to prevent multiple clicks, I prefer the boolean. But the counter method lets you detect double clicks and handle them separately, if you want that feature.

回答3:

In case anyone is still looking for a way to do this. I found that You can use a boolean.

self.disableSubmitButton= ko.observable(false);
  self.SubmitPayment = function () {
        self.disableSubmitButton(true);
       //your other actions here
        }

Then in your view

data-bind="click:SubmitPayment, disable:disableSubmitButton"

回答4:

I did this with a custom binding:

<button data-bind="throttleClick: function() { console.log(new Date()); }>
    I wont double click quicker than 800ms
</button>

---

ko.bindingHandlers.throttleClick = {
    init: function(element, valueAccessor) {
        var preventClick = false;
        var handler = ko.unwrap(valueAccessor());

        $(element).click(function() {
            if(preventClick)
                return;

            preventClick = true;
            handler.call();
            setTimeout(function() { preventClick = false; }, 800);
        })
    }
}