Reduce image size with Sharp

index.js

const sharp = require('sharp');
const fs = require('fs');

const input = sharp('./image.jpg');

input
    .flatten(
        {
            r: 255,
            g: 255,
            b: 255
        }
    )
    .jpeg(
        {
            chromaSubsampling: '4:4:4',
            quality: 100 * 0.75,
            progressive: true,
            force: true
        }
    )
    .withMetadata()
    .toBuffer()
    .then(
        output => {
            console.log(output);
            fs.writeFileSync('output.jpg', output);
        }
    )
    .catch(
        err => {
            console.log(err);
        }
    );