Build Swap Applications on EVM: A Comprehensive Guide

There are two primary approaches to building swap applications with OKX DEX on EVM networks:

1. The API-first approach - Directly interacting with OKX DEX API endpoints
2. The SDK approach - Using the @okx-dex/okx-dex-sdk package for a simplified developer experience

This guide covers both methods to help you choose the best approach for your project's requirements.

Method 1: API-First Approach

This section demonstrates executing a token swap using OKX DEX API endpoints directly. We'll use a USDC to ETH swap on Ethereum as our example.

1. Setting Up Your Development Environment

2. Checking Token Allowance

For ERC20 tokens (not native tokens like ETH), you must verify if the token has been approved for DEX spending.

3. Managing Token Approvals

If the current allowance is insufficient for your swap amount:

3.1 Defining Approval Parameters

3.2 Creating Helper Functions

3.3 Calculating Gas Limit

Two methods available:

• Using standard RPC calls
• Via Onchain Gateway API (enterprise feature)

3.4 Sending Approval Transactions

4. Obtaining Quote Data

4.1 Configuring Quote Parameters

4.2 Implementing Helper Functions

5. Preparing Swap Transactions

5.1 Defining Swap Parameters

5.2 Requesting Transaction Data

6. Transaction Simulation

Crucial for verifying successful execution before broadcasting:

7. Broadcasting Transactions

Two primary methods:

1. Enterprise Solution: Using Onchain Gateway API
2. Standard Method: Via Web3 RPC calls

8. Transaction Tracking

Two approaches:

• Onchain Gateway API (enterprise)
• Standard SWAP API endpoint

9. Complete Implementation Example

10. MEV Protection Strategies

MEV Protection via Broadcast API

Enterprise customers can enable this feature through API parameters:

Basic Configuration:

{
  "extraData": {
    "enableMevProtection": true
  }
}

Integration Example

// Sample integration code demonstrating MEV protection

Method 2: SDK Approach

Simplifies development while maintaining full functionality:

1. SDK Installation

npm install @okx-dex/okx-dex-sdk

2. Environment Configuration

API_KEY=your_key_here
PRIVATE_KEY=your_wallet_key

3. Client Initialization

// Sample client initialization code

4. Token Approval Process

// Approval utility function implementation

5. Executing Swaps

// Complete swap execution example

6. Advanced SDK Features

• Simplified quote retrieval
• Enhanced transaction management
• Built-in error handling

FAQs

Q: Which approach is better for beginners?
A: The SDK approach is generally more beginner-friendly as it handles many complex implementation details.

Q: What are the benefits of the API-first approach?
A: Greater flexibility and control, especially for custom implementations.

Q: How does MEV protection work?
A: The system uses advanced transaction routing strategies to minimize exposure to front-running.

Q: Is enterprise API access required for basic functionality?
A: No, only advanced features like Onchain Gateway require enterprise access.

Q: What chains are supported?
A: All major EVM chains including Ethereum, BSC, and Base.

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