How to expand children of a node using user handle in JavaScript Diagram layout?

This article explains how to expand the children of a node using a user handle in a JavaScript Diagram layout. In the JavaScript Diagram layout, we can expand and collapse a large number of nodes with the expand and collapse feature. Additionally, we can achieve the expansion and collapse of child nodes by clicking on user handles. To achieve this, we utilize a method to filter the parent ID from the data source and dynamically modify the diagram’s data source.

//initialise handle
let handle = [
 {
   name: 'child',
   tooltip: { content: 'Add child' },
   pathData:
     'M6.09,0 L13.75,6.88 L6.09,13.75 L6.09,9.64 L0,9.64 L0,4.11 L6.09,4.11 Z  ',
   visible: true,
   offset: 0.5,
   side: 'Bottom',
   margin: { top: 0, bottom: 0, left: 0, right: 0 },
 },
];
let diagram: Diagram = new Diagram({
 selectedItems: {
   constraints: SelectorConstraints.All | SelectorConstraints.UserHandle,
   userHandles: handle as any,
 },
 onUserHandleMouseDown: function (args) {
   let selectedNode = diagram.selectedItems.nodes[0];
   let id = (selectedNode.data as any).Id;
   render(id);
 },
});
diagram.appendTo('#diagram');

The filter function takes an ID as a parameter and filters the data source dynamically based on the ID. It filters the data to include only those nodes whose ‘Manager’ property matches the provided ID. It utilizes a lookup object (idLookup) to store existing IDs and ensures that duplicate IDs are not added to the data source. The filtered data is then appended to the existing data source of the diagram, and the diagram is updated using the dataBind method.

//method to render child nodes
function render(id: string) {
 let datasource = diagram.dataSourceSettings.dataSource.dataSource.json;
 let filteredData = diagramData.filter((item) => item.Manager === id);

 // Lookup object to store existing IDs
 const idLookup = {};
 datasource.forEach((item) => {
   idLookup[(item as any).Id] = true;
 });

 filteredData = filteredData.filter((item) => !idLookup[item.Id]);

 Array.prototype.push.apply(datasource, filteredData);
 diagram.dataSourceSettings.dataSource = new DataManager(datasource);
 diagram.dataBind();
}

Refer to the working sample for additional details and implementation: Sample

Conclusion

We hope you enjoyed learning about how to expand the children of a node using a user handle in the JavaScript Diagram layout.

You can refer to our JavaScript Diagram feature tour page to learn about its other groundbreaking feature representations and documentation, as well as how to quickly get started with configuration specifications. You can also explore our JavaScript Diagram example to understand how to create and manipulate data.
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