PdfCheckBoxStyle API in JavaScript PDF API control

// Load an existing PDF document
let document: PdfDocument = new PdfDocument(data, password);
// Access check box field
let field: PdfCheckBoxField = document.form.fieldAt(0) as PdfCheckBoxField;
// Access first item of check box field
let item: PdfStateItem = field.itemAt(0) as PdfStateItem;
// Sets the check box style as check
item.style = PdfCheckBoxStyle.check;
// Save the document
document.save('output.pdf');
// Destroy the document
document.destroy();