IndexPrinter.js

function Indexer (object, separator) {
    this.separator = separator || /\|/;
    this.list = typeof object === "string" ? object.split('\n') : [];
}

/***
* Returns true if the given key is found.
*/
Indexer.prototype.containsKey = function (key) {
    this.key = key;
    return this.list.filter(findKey, this).length !== 0;
};

/***
* Returns value if the given key is found.
*/
Indexer.prototype.getValue = function (key) {
    if (!this.containsKey(key)) {
      console.log("Did not find key: " +key);
      return null;
    } else {
      console.log("Found key: " +key);
    }

    this.key = key;
    var result = this.list.filter(findKey, this)[0].split(this.separator)[1];
    console.log("Got item: " +result);
    return result;
};

/***
* Helper filter function
*/
var findKey = function(element, index, array) {
  return this.key === element.split(this.separator)[0];
};

module.exports = Indexer;

See https://gist.github.com/varl/5403312 for the tests for this class.