This little utility changes the "width" (i.e. of a progress bar) with sense of unpredictability. The obj implementation is just to make it generic-ish (was originally a React component method.) The only logic that's been tested is marked below as "the meat"

fake_progress_bar_width.js

const obj = {
  width: 0,
  start() {
    let extra = 0;
    let interval = setInterval(() => {
      if (width === 100) {
        clearInterval(interval);
      }
      // the meat
      if (Math.floor(Math.random() + 0.6)) {
          this.width = this.width + (3 + extra) + (Math.floor(Math.random() * 6));
          extra = 0;
      } else {
        extra += 3;
      }
    }, 1000);
  }
}