manage-multitask.js

const exec = require('child_process').exec;

StartMultipleTasks = () => {
  new StartSingleTask(0).download();
  new StartSingleErrorTask(1).download();
  new StartSingleTask(2).download();
  new StartSingleTask(3).download();
  new StartSingleTask(4).download();
  new StartSingleErrorTask(5).download();
  new StartSingleTask(6).download();
  new StartSingleErrorTask(7).download();
}


class StartSingleTask {
  constructor(index) {
    this.index = index;
  }
  download()  {
    exec('wget "http://www.w3schools.com/css/trolltunga.jpg" -O output1.jpg', function (error, stdout, stderr) {
      if (error) {
        console.log(this.index + " Failed");
        return;
      }
      else
        console.log(this.index + " Succeeded.");
    }.bind(this));
  }
}

class StartSingleErrorTask {
  constructor(index) {
    this.index = index;
  }
  download() {
    exec('wget "http://www.w3schools.com/css/trolltunaga.jpg" -O output1.jpg', function (error, stdout, stderr) {
      if (error) {
        console.log(this.index + " Failed");
        return;
      }
      else
        console.log(this.index + " Succeeded.");
    }.bind(this));
  }
}

StartMultipleTasks();