Range check - onchange

Check range of checkboxes in knockout.js via onchange

by keddie

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.7.0/underscore-min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
    <thead>
        <tr>
            <th colspan="2">Control</th>
            <th>Values</th>
            <th>Name</th>
        </tr>
    </thead>
    <tbody data-bind="foreach: values">
        <tr>
            <td>
                <input type="checkbox" data-bind="checked: $data.isSelected"></input>
            </td>
            <td>
                <input type="checkbox" data-bind="click: $root.checkboxesModel.handleSelectionEvent, attr: { checked: $data.isSelected }"></input>
            </td>
            <td data-bind="text: $data.isSelected">a</td>
            <td data-bind="text: $data.name"></td>
        </tr>
    </tbody>
</table>

JavaScript

var GeneralModel = function() {
  this.values = [
    { isSelected: ko.observable(false), name: "a" },
    { isSelected: ko.observable(false), name: "b" },
    { isSelected: ko.observable(false), name: "c" },
    { isSelected: ko.observable(false), name: "d" },
    { isSelected: ko.observable(false), name: "e" },
    { isSelected: ko.observable(false), name: "f" }
  ];
  var config = {
    collection: this.values,
    limit: 8,
    limitMsg: "",
    checkFirst: false
  };
  this.checkboxesModel = new CheckboxesModel(config);
}

/**
 * Checkboxes model for range, exlusive etc. selection
 * @param {array} config
 */
var CheckboxesModel = function (config) {
    this.collection = ko.observable( config.collection );
    this.lastChecked = ko.observable(null);
    this.limit = config.limit;
    this.checkedNum = 0;

    this.turnSelection = function(index1, index2, value) {
        var start = index1 < index2 ? index1 : index2;
        var end = index1 < index2 ? index2 : index1;
        for(var i = start; i <= end; i++) {
             if(this.checkedNum > this.limit) {
               return false;
             }

             this.collection()[i].isSelected(value);

             if(value) {
               this.checkedNum++;
             } else {
               this.checkedNum--;
             }
        }
        return true;
    }.bind(this);

    this.turnOffAll = function() {
      this.turnSelection(0,this.collection().length-1, false);
    }.bind(this);

    this.turnOnAll = function() {
      this.turnSelection(0,this.collection().length-1, true);
    }.bind(this);

    this.handleSelectionEvent = function (data, event) {
        if (event.shiftKey) {
            var clicked = _.indexOf(this.collection(), data);
            if (_.isNull(this.lastChecked())) {
                return this.turnSelection(0, clicked, true);
            } else {
                var index = _.indexOf(this.collection(), this.lastChecked());
                return...