retrieval/src/util/reverse_index.js

Full text search engine in js. Features BM25 ranking function that can be tuned.

/**
 * Inverts an array into an object. This new object's keys are the array,
 * and its values are the indexes of that array.
 */
const _ = require('lodash');

module.exports = function(arr_, transform_) {
    return _.mapValues(_.invertBy(arr_),
                       function(value) {
                          return transform_(value);
                       });
};