purchase

window.dataLayer = window.dataLayer || [];
window.dataLayer.push({ ecommerce: null });
window.dataLayer.push({
  event: 'purchase',            // name of the event. In this case, it always must be purchase
  ecommerce: {
    currency: 'EUR',
    value: 29.98,                       // order total (price of all products). If you want, it can be only price of all products
    tax: 3.00,                          // tax
    shipping: 5.00,                 // shipping costs
    transaction_id: 'abc123',           // transaction id
    coupon: 'ENDOFSUMMER',          // if coupon was applied to the order, include it here
    items: [{                           // an array with all products
      item_name: 'Product 1',           // insert an actual product name
      item_id: 'product1',              // insert an actual product ID
      price: 11.99,                    // insert an actual product price. Number or a string. Don't include currency code
      affiliation: 'My online shop',    // affiliation (e.g. affiliate id, name of the store, etc.)
      item_brand: 'brand A',            // insert an actual product brand
      item_category: 'Apparel',         // insert an actual product top-level category
      item_category2: 'T-shirt',        // if it is possible to drill down the categories (e.g. Apparel, then T-shirt, then Men), use item_category2, item_category3, etc. Can use from item_category up to item_category5
      item_variant: 'Blue',             // insert an actual product variant
      quantity: 1,                      // product quantity
      item_coupon: 'SUMMER20'           // if a coupon was applied not to the entire order but to one product, use item_coupon
    },{
      item_name: 'Product 2',
      item_id: 'product2',
      price: 12.99,
      affiliation: 'My online shop',
      item_brand: 'Brand B',
      item_category: 'Category B',
      item_variant: 'Yellow',
      quantity: 1
    }]
  }
});