# Prevent Event Overlap (JavaScript Scheduler) | DayPilot Pro for JavaScript Demo

> You can forbid [event overlapping](https://doc.daypilot.org/scheduler/event-overlapping/).

## Links

- Canonical HTML: /demo/scheduler/eventoverlapping.html
- Source HTML folder: /demo/scheduler/
- Catalog root: /demo/
- Catalog: /demo/llms.txt

## Source

### Inline demo script 1

```javascript
const dp = new DayPilot.Scheduler("dp", {
            startDate: "2026-01-01",
            days: 365,
            scale: "Day",
            timeHeaders: [
                {groupBy: "Month", format: "MMMM yyyy"},
                {groupBy: "Cell", format: "d"}
            ],
            allowEventOverlap: false,
            treeEnabled: true,
            resources: [
                {name: "Room A", id: "A"},
                {name: "Room B", id: "B"},
                {name: "Room C", id: "C"},
                {name: "Room D", id: "D"},
                {name: "Room E", id: "E"},
                {name: "Room F", id: "F"},
                {name: "Room G", id: "G"},
                {name: "Room H", id: "H"},
                {name: "Room I", id: "I"},
                {name: "Room J", id: "J"},
                {name: "Room K", id: "K"},
            ],
            onTimeRangeSelected: args => {
                const name = prompt("New event name:", "Event");
                dp.clearSelection();
                if (!name) return;
                const e = new DayPilot.Event({
                    start: args.start,
                    end: args.end,
                    id: DayPilot.guid(),
                    resource: args.resource,
                    text: name
                });
                dp.events.add(e);
                dp.message("Created");
            },
            eventDeleteHandling: "Update",
        });
        dp.init();
        dp.scrollTo("2026-03-25");

        const app = {
            init() {
                this.loadEventData();
            },
            loadEventData() {
                const events = [];

                for (let y = 1; y < 5; y++) {
                    const offset = Math.floor(Math.random() * 2) + 0; // 0 to 2
                    let first = new DayPilot.Date("2026-03-25T00:00:00").addDays(offset);
                    for (let i = 0; i < 15; i++) {
                        const duration = Math.floor(Math.random() * 6) + 1; // 1 to 6
                        const start = Math.floor(Math.random() * 3) + 1; // 1 to 3

                        const e = {
                            start: first.addDays(start),
                            end: first.addDays(start).addDays(duration),
                            id: DayPilot.guid(),
                            resource: String.fromCharCode(65 + y),
                            text: "Event"
                        };

                        events.push(e);

                        first = e.end;
                    }
                }
                dp.update({events});
            }
        };
        app.init();
```