columns.width String|Number

The width of the column. Numeric values are treated as pixels.

Example - setting the column width as a string

<div id="treelist"></div>
<script>
  $("#treelist").kendoTreeList({
    columns: [
      { field: "lastName", width: "200px" },
      { field: "position" }
    ],
    dataSource: {
      data: [
        { id: 1, parentId: null, lastName: "Jackson", position: "CEO" },
        { id: 2, parentId: 1, lastName: "Weber", position: "VP, Engineering" }
      ]
    }
  });
</script>

Example - setting the column width as a number

<div id="treelist"></div>
<script>
  $("#treelist").kendoTreeList({
    columns: [
      { field: "lastName", width: 200 },
      { field: "position" }
    ],
    dataSource: {
      data: [
        { id: 1, parentId: null, lastName: "Jackson", position: "CEO" },
        { id: 2, parentId: 1, lastName: "Weber", position: "VP, Engineering" }
      ]
    }
  });
</script>

To set the column width after the TreeList initialization you can use the setOptions() method.