Mocha report to contain only failed cases

I want to cofigure mocha report to only contain failed cases. I am using below code to read js test files and send mail on completion . I want to send only failure cases. How to configure it in mocha ?

const Mocha = require('mocha');
const fs = require('fs');
const path = require('path');
const mocha = new Mocha({});
const sendMail = require('./sendMail');
const error = require('./errMsg');

async function executeMocha() {
    const testDirPath = path.resolve('./') + '/test';
    fs.readdirSync(testDirPath).filter(function (file) {
        // Only keep the .js files
        return file.substr(-3) === '.js';
    }).forEach(function (file) {
        mocha.addFile(
            path.join(testDirPath, file)
        );
    });

    mocha.reporter('mocha-simple-html-reporter', { output: '/tmp/testspec.html' }).run(
        async (err,res) => {
            if(err){
                console.log("\n\n\n\nTest Case FAAAAAAAAAAILLLLLL \n\n\n\n");
            }
            console.log("\n\n\n\nTest Case Execution Successfull\n\n\n\n");
            await getResult();
        }
    );
}

async function getResult() {
    fs.readFile(('/tmp/testspec.html'), 'utf8', async (err, res) => {
        if (err) {
            await sendMail((process.env.env_type +error.fail.subject + process.env.CB_TEST_URL ), error.fail.body + err);
        }
        await sendMail((process.env.env_type +error.success.subject + process.env.CB_TEST_URL ), res);
    })
}

module.exports = executeMocha

from Mocha report to contain only failed cases