Why does one work for one javascript but doen't work for other

  $: 'jquery/src/jquery',
    jquery: 'jquery/src/jquery',

    jQuery: 'jquery/src/jquery',
    'window.jQuery': 'jquery',
    Popper: ['popper.js', 'default']

why does the one above work for one javascript but for other javascript to work I have to have this

  $: 'jquery',
  jQuery: 'jquery',
  'window.jQuery': 'jquery',
  Popper: ['popper.js', 'default']

This is in the environment.js