# E-commerce Checkout Flow Reference

## Complete Checkout Event Sequence

```
view_cart → begin_checkout → add_shipping_info → add_payment_info → purchase
```

Each step must fire in order with consistent item data.

## Event Details

### 1. view_cart
When user views cart page.

```javascript
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: "view_cart",
  ecommerce: {
    currency: "KRW",
    value: 125000,
    items: [{
      item_id: "SKU_001",
      item_name: "Blue T-Shirt",
      price: 45000,
      quantity: 2,
      item_brand: "Brand",
      item_category: "Apparel"
    }, {
      item_id: "SKU_002",
      item_name: "Black Jeans",
      price: 35000,
      quantity: 1
    }]
  }
});
```

### 2. begin_checkout
When user initiates checkout process.

```javascript
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: "begin_checkout",
  ecommerce: {
    currency: "KRW",
    value: 125000,
    coupon: "SUMMER10",
    items: [/* same items as view_cart */]
  }
});
```

### 3. add_shipping_info
When user completes shipping step.

```javascript
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: "add_shipping_info",
  ecommerce: {
    currency: "KRW",
    value: 125000,
    coupon: "SUMMER10",
    shipping_tier: "Express",  // Required
    items: [/* same items */]
  }
});
```

**shipping_tier values:**
- "Standard" / "일반배송"
- "Express" / "익일배송"  
- "Same Day" / "당일배송"
- "Free" / "무료배송"
- "Store Pickup" / "매장픽업"

### 4. add_payment_info
When user enters payment details.

```javascript
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: "add_payment_info",
  ecommerce: {
    currency: "KRW",
    value: 125000,
    coupon: "SUMMER10",
    payment_type: "Credit Card",  // Required
    items: [/* same items */]
  }
});
```

**payment_type values:**
- "Credit Card" / "신용카드"
- "Debit Card" / "체크카드"
- "Bank Transfer" / "계좌이체"
- "Virtual Account" / "가상계좌"
- "Mobile Payment" / "휴대폰결제"
- "Kakao Pay" / "카카오페이"
- "Naver Pay" / "네이버페이"
- "Toss" / "토스"
- "PayPal"

### 5. purchase
When transaction completes successfully.

```javascript
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: "purchase",
  ecommerce: {
    transaction_id: "T_20250115_001234",  // Required, unique
    value: 130500,                         // Required (total)
    tax: 11863,
    shipping: 5000,
    currency: "KRW",                       // Required
    coupon: "SUMMER10",
    items: [{
      item_id: "SKU_001",
      item_name: "Blue T-Shirt",
      affiliation: "Online Store",
      coupon: "SUMMER10",
      discount: 4500,
      price: 45000,
      quantity: 2
    }]
  }
});
```

## Funnel Drop-off Analysis

### Tracking Drop-offs
Monitor completion rate at each step:

| Step | Event | Drop-off Indicator |
|------|-------|-------------------|
| Cart | view_cart | User leaves cart page |
| Checkout Start | begin_checkout | User doesn't proceed |
| Shipping | add_shipping_info | Address form abandoned |
| Payment | add_payment_info | Payment not completed |
| Complete | purchase | Transaction failed |

### Implementing Drop-off Tracking

```javascript
// Track checkout step viewed but not completed
let checkoutStep = 0;

function trackCheckoutProgress(step) {
  if (step > checkoutStep) {
    checkoutStep = step;
  }
}

window.addEventListener('beforeunload', () => {
  if (checkoutStep > 0 && checkoutStep < 5) {
    dataLayer.push({
      event: 'checkout_abandon',
      last_step: checkoutStep,
      step_name: ['cart', 'checkout', 'shipping', 'payment', 'complete'][checkoutStep - 1]
    });
  }
});
```

## Value Consistency Check

Ensure `value` matches across events:

```
view_cart.value = sum(items.price * items.quantity)
begin_checkout.value = view_cart.value
add_shipping_info.value = begin_checkout.value
add_payment_info.value = add_shipping_info.value
purchase.value = add_payment_info.value + shipping + tax - discount
```

## Common Issues

### Duplicate Purchase Events
**Problem**: Same order tracked multiple times
**Solution**:
```javascript
// Check if already tracked
const txId = "T_12345";
if (!sessionStorage.getItem('purchase_' + txId)) {
  dataLayer.push({ event: 'purchase', ... });
  sessionStorage.setItem('purchase_' + txId, 'true');
}
```

### Missing Items in Later Steps
**Problem**: Items present in view_cart but missing in purchase
**Solution**: Store cart data in session and reuse

### Inconsistent Currency
**Problem**: Some events use USD, others KRW
**Solution**: Standardize currency across all events

### Wrong Value Calculation
**Problem**: purchase.value doesn't include tax/shipping
**Solution**: 
```
purchase.value = subtotal + tax + shipping - discount
```

## Korean E-commerce Platforms

### Cafe24
Custom dataLayer variable names - check documentation

### Shopify Korea
Standard GA4 format with `Shopify.checkout` object

### WooCommerce
Use official GA4 plugin or custom implementation

### Naver SmartStore
Separate Naver Analytics implementation required

## Checkout Flow Checklist

- [ ] view_cart fires on cart page load
- [ ] begin_checkout fires on checkout button click
- [ ] add_shipping_info includes shipping_tier
- [ ] add_payment_info includes payment_type
- [ ] purchase has unique transaction_id
- [ ] All events have consistent items array
- [ ] Currency is consistent across all events
- [ ] Value calculations are accurate
- [ ] ecommerce object cleared before each push
- [ ] Purchase event fires only once per order
