How to get max-age value from cache-control header using request in Nodejs?

Question

I am using request to request a page with the following code:

request(url, { json: true }, (err, res, body) => {
    if (err) {
        return null
    } else {
        console.log("res", res.headers["cache-control"]);
    }
})

I can get the cache-control header this way. But how do I get the max-age value which is in cache-control header, like cache-control: public, max-age=20140, must-revalidate, no-transform ? Is there any shorthand or do I have to do string manipulations?

Answer 1

There is no shorthand - headers are simply key/value pairs and there are no standard libraries in JS to parse structured header values.

You could just use a regex to pull out the number:

const headers = {
  'cache-control': 'public, max-age=20140, must-revalidate, no-transform'
}

const matches = headers['cache-control']?.match(/max-age=(\d+)/)

const maxAge = matches ? parseInt(matches[1], 10) : -1

console.log(maxAge)