How to add additional files to CRA WorkBox Precache?

Question

So, I want to make a PWA for one of my CRA projects. The app has a different wallpaper everytime it loads, which it gets through an API. But since PWAs are supposed to have offline support, I wanted to have a fallback wallpaper which is cached. Or, even better the last result from the API is cached and returned till the user is offline. Something of a StaleWhileRevalidate strategy. But I can't figure out how to achieve this without ejecting from create-react-app. Any ideas?

Thanks

Answer 1

Ok, I figured it out myself. In case anyone else needs this, you can create a file named add_to_precache.js in your project's root directory and add the following code to it:

let fs = require('fs');
let build_dir = "./build";
let precache_re = /precache-manifest\.[a-zA-Z0-9]*\.js/

let urls_to_add = [
   /*
 Path to files you want to add relative to build directory. Along with any other homepage value you have. Eg: "/app/background.jpg"
*/
]

function generate_revision(){
    var chars = "abcdefghijklmnopqrstuvwxyzABCDEEFGHIJKLMNOPQRSTUVWXYZ0123456789".split('');
    var revision = '';
    for(let i=0;i<24;i++){
        revision += chars[Math.round(Math.random() * 62)];
    }
    return revision;
}


fs.readdir(build_dir, (err, files) => {
    for(let file of files){
        if(precache_re.test(file)){
            let cont = fs.readFileSync(build_dir + '/' + file).toString()
            cont = cont.slice(0, cont.length - 4)

            urls_to_add.forEach((url) => {
                cont += `,\n  {\n    "url": "${url}",\n    "revision": "${generate_revision()}"\n  }`
            })

            cont += `\n]);`
            fs.writeFileSync(build_dir + '/' + file, cont);
            break;
        }
    }
})

And then modify your package.json from

//....
"scripts": {
   //....
   "build": "react-scripts build"
   //...
}
//...
}

to

//....
"scripts": {
   //....
   "build": "react-scripts build && node add_to_precache"
   //...
}
//...
}

And you are done. It will do the trick when building the application