Advanced version of script injection script

Inject any lib.js

// a. CDN like jsdelivr.com can load multiple script with one url
// b. predicate condition can be omit
var scripts2Load = [{ 'name': name, url: "", 'predicate': () => true }];
// Example:
//var scripts2Load = [{ 'name': 'Lodash', 
//url: 'https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)', 
//'predicate': () => window._ }];
((window) => {
  // Change it if you want.
  const timeout = 2000;
  // Helper
  const logger = msg => msg && console.log(msg);
  const injector = url => {
    const tag = document.createElement('script');
    tag.src = url;
    window.document.getElementsByTagName('head')[0].appendChild(tag);
  };
  // Turn scripts2Load to Promises
  const promisify = toLoad => {
    return new Promise((resolve, reject) => {
      logger(`Now injecting ${toLoad.name}...`);
      injector(toLoad.url);
      const defer = time => {
        if (toLoad.predicate()) {
          resolve(toLoad);
        } else {
          setTimeout(() => {
            logger(`Detecting ${toLoad.name}\t Wait:${time}`);
            if (time < timeout) defer(time + 50);
          }, 50);
        }
        reject(toLoad);
      };
      defer(0);
    });
  };
  Promise.all(scripts2Load.map(promisify))
    .then(toLoads => toLoads.map(toLoad => logger(`Lib ${toLoad.name} is loaded sucessfully!`)))
    .catch(console.error);
})(window);

Inject any lib.md

Intro

A advanced version of Inject Lo-dash FP or Ramda to browser, see more there.

Features

• Allows u inject many libs concurently.
• Also handle all the callbacks using "promise".

Disclaimer

1. Check whether your browser supports ES6 features or not first.
2. I hornestly don't know if I implement "Promise" correctly or not. It turns out that I am still handling all the timeout / detection myself. Despite the functional programming tactics are very helpful, I reckon my implementation is still verbose and ugly. Especially the recursion of defer() function! That is my limitation. I am kean to see if there is a better solution:smile:!
3. Because this script will almost always runs on 3rd-party pages, we cannot rely on any fancy polyfill dependency. (Like bluebird.js)