overleaf/services/web/frontend/js/main/post-gateway.js

define(['../base'], App =>
  App.controller('PostGatewayController', function($scope) {
    $scope.handleGateway = function() {
      const { params } = JSON.parse($('#gateway-data').text())
      params.viaGateway = 'true'
      Object.keys(params).forEach(param => {
        $('<input>')
          .attr({
            type: 'hidden',
            name: param,
            value: params[param]
          })
          .appendTo('#gateway')
      })
      $('#gateway').submit()
    }
  }))