can't read property addWidget of undefined with JSON and gridstack

问题

Running into a problem with my attempt to build a gridstack dash

I get "Uncaught TypeError: Cannot read property 'addWidget' of undefined" when trying to load the page.. (the code is based on the basic gridstack serialized demo https://github.com/gridstack/gridstack.js/blob/develop/demo/serialization.html)

my changed script section is

    <script type="text/javascript">
    $(function() {
        var options = {};
        $('.grid-stack').gridstack(options);
        new function() {

            this.grid = $('.grid-stack').data('gridstack');

            this.loadGrid = function() {
                this.grid.removeAll();
                debugger;
                const URL = `//${window.location.hostname}/dashboard/getDashboard`;
                $.getJSON(URL, function(items) {
                    _.each(items, function(node) {
                        this.grid.addWidget($('<div><div class="grid-stack-item-content" /></div>'),
                            node.x, node.y, node.width, node.height, true, 4, 12, 1, 8, node.id);
                    }.bind(this));
                });
                return false;
            }.bind(this);

            this.saveGrid = function() {
                this.serializedData = _.map($('.grid-stack > .grid-stack-item:visible'), function(el) {
                    el = $(el);
                    var node = el.data('_gridstack_node');
                    return {
                        x: node.x,
                        y: node.y,
                        width: node.width,
                        height: node.height
                    };
                });
                $('#saved-data').val(JSON.stringify(this.serializedData, null, '    '));
                return false;
            }.bind(this);

            this.clearGrid = function() {
                this.grid.removeAll();
                return false;
            }.bind(this);
            $('#save-grid').click(this.saveGrid);
            $('#load-grid').click(this.loadGrid);
            $('#clear-grid').click(this.clearGrid);
            this.loadGrid();
        };
    });
</script>

Any suggestions? I've tried a number of things, but keep getting dead ends

Best I can work out is this.grid disappears as I enter getJSON

Data loads fine BTW, I see items populated with the data I expect.

回答1:

It seems like the context of this in the loadGrid method may be incorrect, try changing it to this:

this.loadGrid = function () {
  this.grid.removeAll();
  debugger;
  const URL = `//${window.location.hostname}/dashboard/getDashboard`;
  const context = this;
  $.getJSON(URL, function (items) {
    _.each(items, function (node) {
      context.grid.addWidget($('<div><div class="grid-stack-item-content" /></div>'),
        node.x, node.y, node.width, node.height, true, 4, 12, 1, 8, node.id);
    }.bind(this));
  });
  return false;
}.bind(this);

If you don't use the proper context, this will refer to something else inside those nested functions, either $ or _ possibly.

来源：https://stackoverflow.com/questions/54287633/cant-read-property-addwidget-of-undefined-with-json-and-gridstack

标签

javascript

getjson

gridstack