PercentComplete

<script>
var parentTask = new kendo.data.GanttTask({
    id: 1,
    title: "Parent",
    percentComplete: 0.55,
    start: new Date("2014/6/17 9:00"),
    end: new Date("2014/6/17 11:00")
});
/* The result can be observed in the DevTools(F12) console of the browser. */
console.log(parentTask.percentComplete); // outputs "0.55"
</script>