Injecting HTML

Bitburner uses React and Material-UI to render everything. Modifying the UI is possible but not officially supported.
To automatically enter commands in the terminal (only works if looking at the terminal):
// Acquire a reference to the terminal text field
const terminalInput = document.getElementById("terminal-input");
// Set the value to the command you want to run.
terminalInput.value="home;connect n00dles;home;connect n00dles;home;";
// Get a reference to the React event handler.
const handler = Object.keys(terminalInput)[1];
// Perform an onChange event to set some internal values.
terminalInput[handler].onChange({target:terminalInput});
// Simulate an enter press
terminalInput[handler].onKeyDown({key:'Enter',preventDefault:()=>null});
To add lines to the terminal (only works if looking at the terminal):
<pre>
// Acquire a reference to the terminal list of lines.
const list = document.getElementById("generic-react-container").querySelector("ul");
// Inject some HTML.
list.insertAdjacentHTML('beforeend',`whatever custom html`)