//HTML
<label>
     Check all
     <input id="checker1" type="checkbox"  />
</label>

// JS

  document.getElementById("checker1").addEventListener("click", function (e) {
    theGrid.rows.forEach((r) => {
      if (r.isSelected === true) {
        r.isSelected = false;
      } else if (r.isSelected === false) {
        r.isSelected = true;
      }
    });
    theGrid.refresh();
  });

  function getData(count) {
    var countries = "US,Germany,UK,Japan,Italy,Greece".split(",");
    var products = "Widgets,Gadgets,Yahoos".split(",");
    var data = [];
    for (var i = 0; i < count; i++) {
      var item = {
        id: i,
        country: pickOne(countries),
        product:i % 2 != 0,
        discount: Math.random() * 0.3,
        downloads: Math.round(Math.random() * 200000),
        sales: i % 2 != 0,

      };
      data.push(item);
    }
    return data;
  }
 
(...)

let theGrid = new wijmo.grid.FlexGrid("#theGrid", {
    itemsSource: view,
    deferResizing: true,
    showMarquee: true,
    alternatingRowStep: 0,
    autoGenerateColumns: false,
    columns: [
      { binding: "id", header: "ID", isReadOnly: true },
      { binding: "country", header: "Country" },
      { binding: "product", header: "Product",dataType: wijmo.DataType.Boolean  },
      { binding: "discount", header: "Discount", format: "p0" },
      { binding: "downloads", header: "Downloads" },
      { binding: "sales", header: "Sales", dataType: wijmo.DataType.Boolean},

    ],
  });

(...)
 let checker = new wijmo.grid.selector.BooleanChecker(
    theGrid.columns.getColumn("product")
  );

  let checker2 = new wijmo.grid.selector.BooleanChecker(
    theGrid.columns.getColumn("sales")
  );