script.js

window.onload = () => {
    const [input, output] = document.querySelectorAll('.codemirror-textarea');
    const [run, clear] = document.querySelectorAll('button');

    const editor = CodeMirror.fromTextArea(input, { lineNumbers: true });
    const shell = CodeMirror.fromTextArea(output, { lineNumbers: false });

    run.addEventListener('click', () => {
        const codeToRun = editor.getValue();
        try{
            shell.replaceRange('$ ' + eval(`${codeToRun}`) + '\n', CodeMirror.Pos(shell.lastLine()));
        } catch(e){
            shell.replaceRange('$ ' + e + '\n', CodeMirror.Pos(shell.lastLine()));
        }
    });
    clear.addEventListener('click', () => {
        shell.setValue('')
    });
}