Database in JsStore is an object which contains name of database and list of tables.

Syntax :-

var database = {
    name: "database name",
    tables: [table1, table2, table3]
}

Example :-

var tblProduct = {
    name: 'Product',
    columns: {
        // Here "Id" is name of column 
        Id:{ primaryKey: true, autoIncrement: true },
        ItemName:  { notNull: true, dataType: "string" },
        Price:  { notNull: true, dataType: "number" },
        Quantity : { notNull: true, dataType: "number" }
    }
};

var tblOrder = {
    name: 'Order',
    columns: {
        // Here "OrderId" is name of column 
        OrderId:{ primaryKey: true, autoIncrement: true }
    }
};

var db = {
      name: dbName,
      tables: [tblProduct, tblOrder]
}

Please read initiate database doc for knowing how to use database schema.