numberToCategory.js

/**
 * Classify a numeric input.
 *
 * @param {Number} value
 *   The number to classify.
 * @param {Object/Number[]} [buckets=[-2, -2/3, 2/3, 2]]
 *   An object or numeric array used to classify `value`. If `buckets` is an
 *   array, the returned category will be the first of "very low," "low,"
 *   "medium," and "high," in that order, where the correspondingly ordered
 *   bucket value is higher than the `value` being classified, or "very high"
 *   if all bucket values are smaller than the `value` being classified. If
 *   `buckets` is an object, its values will be sorted, and the returned
 *   category will be the key of the first bucket value that is higher than the
 *   `value` being classified, or the key of the highest bucket value if the
 *   `value` being classified is higher than all the values in `buckets`.
 *
 * @return {String}
 *   The category into which the numeric input was classified.
 */
function numberToCategory(value, buckets) {
    if (!buckets) {
        buckets = [-2, -2/3, 2/3, 2];
    }
    if (typeof buckets.length === 'number' && buckets.length > 3) {
        if (value <  buckets[0]) return 'very low';
        if (value <  buckets[1]) return 'low';
        if (value <  buckets[2]) return 'medium';
        if (value <  buckets[3]) return 'high';
        if (value >= buckets[3]) return 'very high';
    }
    var keys = Object.keys(buckets).sort(function(a, b) {
            return buckets[a] - buckets[b];
        }),
        l = keys.length;
    for (var i = 0; i < l; i++) {
        if (value < buckets[keys[i]]) {
            return keys[i];
        }
    }
    return keys[l-1];
}