As shown in the 3_depositContract.js code discussed in the Sample migration script section, a migration script must export a function using the module.exports syntax:

module.exports = function(deployer) {
  // Deploy contracts using 'deployer'
}

This function should have a deployer object as its first parameter in the function. This object provides methods to deploy the contracts on the blockchain network, and saves the status of the deployed contract for later use in the migration and test scripts. The deployer object should be used for contract deployment for testing, staging, and production. Let's understand how to use the deployer object.