Take an array of objects, and standardize a specific property's value.

standardize-by-key.js

/*
  Standardize data set so that variations of a value can be lumped together with the same property value.
  This function will overwrite properties... Maybe it would be better for it to add a new field.
  
  @param data {object} an array of objects that will be sorted
  @param key {string} the object property to test in every record in the data array
  @param rules {object} an object of arrays defining which values can be combined
  @param combineRest {boolean} whether or not to combined records that do not match any rules
    ⤷ if true, all records that do not match a rule will have their property `key` set to `"other"`
    ⤷ if false, all records that do not match a rule will maintain their existing property `key`
  
  # example
  var data = [
    {color : 'orange', type : 'orange'},
    {color : 'green', type : 'watermelon'},
    {color : 'green', type : 'lime'},
    {color : 'red', type : 'strawberry'}
  ];
  combineByKey(data, 'type', {
    'citrus' : ['orange', 'tangerine', 'lime'],
    'melon' : ['watermelon', 'cantaloupe']
  }, true);
  
  >[
    {color : 'orange', type : 'citrus'},
    {color : 'green', type: 'melon'},
    {color : 'green', type : 'citrus'},
    {color : 'red', type : 'other'}
   ]
*/
const standardizeByKey = (data, key, rules, combineRest) => {
  return data.map((d) => {
    //The current value for the given key
    const val = d[key];

    //The matching value that will replace the current value
    //Will return undefined if no match
    const group = Object.keys(rules).find(r => rules[r].includes(val));

    //New object to merge with existing record. 
    const update = {};

    //Group values by rules, group non-matches into category "other"
    update[key] = group || (combineRest ? 'other' : val);

    //Return the merged object
    return Object.assign({}, d, update)
  });
};