public/javascript/libs/select2.js
function () {
            var val,
                triggerChange = false,
                data = null,
                self = this,
                oldData = this.data();

            if (arguments.length === 0) {
                return this.opts.element.val();
            }

            val = arguments[0];

            if (arguments.length > 1) {
                triggerChange = arguments[1];
            }

            if (this.select) {
                this.select
                    .val(val)
                    .find(":selected").each2(function (i, elm) {
                        data = self.optionToData(elm);
                        return false;
                    });
                this.updateSelection(data);
                this.setPlaceholder();
                if (triggerChange) {
                    this.triggerChange({added: data, removed:oldData});
                }
            } else {
                // val is an id. !val is true for [undefined,null,'',0] - 0 is legal
                if (!val && val !== 0) {
                    this.clear(triggerChange);
                    return;
                }
                if (this.opts.initSelection === undefined) {
                    throw new Error("cannot call val() if initSelection() is not defined");
                }
                this.opts.element.val(val);
                this.opts.initSelection(this.opts.element, function(data){
                    self.opts.element.val(!data ? "" : self.id(data));
                    self.updateSelection(data);
                    self.setPlaceholder();
                    if (triggerChange) {
                        self.triggerChange({added: data, removed:oldData});
                    }
                });
            }
        }
function () {
            var val,
                triggerChange = false,
                data = null,
                self = this,
                oldData = this.data();

            if (arguments.length === 0) {
                return this.opts.element.val();
            }

            val = arguments[0];

            if (arguments.length > 1) {
                triggerChange = arguments[1];
            }

            if (this.select) {
                this.select
                    .val(val)
                    .find(":selected").each2(function (i, elm) {
                        data = self.optionToData(elm);
                        return false;
                    });
                this.updateSelection(data);
                this.setPlaceholder();
                if (triggerChange) {
                    this.triggerChange({added: data, removed:oldData});
                }
            } else {
                // val is an id. !val is true for [undefined,null,'',0] - 0 is legal
                if (!val && val !== 0) {
                    this.clear(triggerChange);
                    return;
                }
                if (this.opts.initSelection === undefined) {
                    throw new Error("cannot call val() if initSelection() is not defined");
                }
                this.opts.element.val(val);
                this.opts.initSelection(this.opts.element, function(data){
                    self.opts.element.val(!data ? "" : self.id(data));
                    self.updateSelection(data);
                    self.setPlaceholder();
                    if (triggerChange) {
                        self.triggerChange({added: data, removed:oldData});
                    }
                });
            }
        }
single