How do I swap two items in an observableArray?

Question

I have a button that moves an item one position left in an observableArray. I am doing it the following way. However, the drawback is that categories()[index] gets removed f

Answer 1

I know this answer comes a bit late, but I thought it might be useful to others who want a more general swap solution. You can add a swap function to your observableArrays like so:

ko.observableArray.fn.swap = function(index1, index2) {
    this.valueWillMutate();

    var temp = this()[index1];
    this()[index1] = this()[index2];
    this()[index2] = temp;

    this.valueHasMutated();
}

You can then use this function to swap two elements in an array given their indices:

myArray.swap(index1, index2);

For a moveUp function, you could then do something like this:

moveUp: function(category) {
    var i = categories.indexOf(category);
    if (i > 0) {
        categories.swap(i, i+1);
    }
}