The truffle.js file is a JavaScript file used to configure the project. This file can execute any code necessary to create the configuration for the project. It must export an object representing your project configuration. Here is the default content of the file:

module.exports = { 
  networks: { 
    development: { 
      host: "localhost", 
      port: 8545, 
      network_id: "*" // Match any network id 
    } 
  } 
};

There are various properties this object can contain. But the most basic one is networks. The networks property specifies which networks are available for deployment as well as specific transaction parameters when interacting with each network (such as gasPrice, from, gas, and so on). The default gasPrice is 100,000,000,000, gas is 4712388, and from is the first available contract in the ethereum client.

You can specify as many networks as you want. Go ahead and edit the configuration file to this:

module.exports = { 
  networks: { 
    development: { 
      host: "localhost", 
      port: 8545, 
      network_id: "10" 
    }, 
    live: { 
         host: "localhost", 
      port: 8545, 
      network_id: "1" 
    } 
  } 
};

In the preceding code, we are defining two networks with the names development and live.