taken from https://github.com/auth0/auth0.js/blob/109f7ad005850bec4c742c437c1ce731b7cd71bb/src/helper/object.js

camelCasingArray.js

function snakeToCamel(str) {
  var parts = str.split('_');
  return parts.reduce(function (p, c) {
    return p + c.charAt(0).toUpperCase() + c.slice(1);
  }, parts.shift());
}

function toCamelCase(object, exceptions) {
  exceptions = exceptions || [];

  return Object.keys(object).reduce(function (p, key) {
    var newKey = exceptions.indexOf(key) === -1 ? snakeToCamel(key) : key;
    p[newKey] = typeof(object[key]) === 'object' ? toCamelCase(object[key]) : object[key];
    return p;
  }, {});
}

console.log(toCamelCase({app_metadata:{groups:["a", "b", "c"]}}))
// outputs: { appMetadata: { groups: { '0': 'a', '1': 'b', '2': 'c' } } }