javascript select all for multi select combo

i have a filter called project. it is a multi select drop downbox. i want to select the {All} check box using the following script ( tableau 8.3 and script file tableau_v8.js )  is not doing it

var placeholderDiv = $("⌗tableauViz"); // document.getElementById("tableauViz");

                var url = "https://dev.tableau./t/TEST/views/Opex";

                var options = {

                    width: "100%",

                    height: "100%",

                    hideTabs: true,

                    hideToolbar: true,

                    Department: "001",

                    "Business Unit": "AC",

                    "Expense Category": "Direct Recharge",

                    Currency: "USD",

                    "Project" : "ALL",

                    onFirstInteractive: function() {

                        workbook = viz.getWorkbook();                    

                                      });

                    }

                };

                viz = new tableau.Viz(placeholderDiv[0], url, options);