Source: collections/Comparer.js

  1. const { EqualityComparer } = require('./EqualityComparer');
  4. /**
  5.  * @template T
  6.  */
  7. class Comparer {
  8.   /**
  9.    * @param {EqualityComparer.<T>} [eqComparer] Optional. Defaults to
  10.    * EqualityComparer.default. An EqualityComparer to use for comparing
  11.    * two items. The method compareTo() returns 0 if the equality comparer
  12.    * considers the two compared items to be equal.
  13.    */
  14.   constructor(eqComparer = EqualityComparer.default) {
  15.     /** @type {EqualityComparer.<T>} */
  16.     this._eqComparer = null;
  17.     this.equalityComparer = eqComparer;
  18.   };
  20.   /**
  21.    * @returns {EqualityComparer.<T>} The current EqualityComparer.
  22.    */
  23.   get equalityComparer() {
  24.     return this._eqComparer;
  25.   };
  27. 	/**
  28. 	 * @access protected
  29. 	 * @param {EqualityComparer.<T>} eqComparer The comparer
  30. 	 * @returns {EqualityComparer.<T>} The same comparer that was given
  31. 	 * @throws {Error} If the given value is not of type EqualityComparer.
  32. 	 */
  33. 	_validateEqualityComparer(eqComparer) {
  34.     if (!(eqComparer instanceof EqualityComparer)) {
  35.       throw new Error(
  36. 				`The value provided is not of type ${EqualityComparer.name}: ${util.inspect(eqComparer)}`);
  37. 		}
  38. 		return eqComparer;
  39. 	};
  41.   /**
  42.    * @param {EqualityComparer.<T>} value An EqualityComparer to use.
  43.    */
  44.   set equalityComparer(value) {
  45. 		this._eqComparer = this._validateEqualityComparer(value);
  46.   };
  48.   /**
  49.    * Compare two items and return a value that indicates which of them
  50.    * is considered to be less or smaller. A negative value means that
  51.    * x is smaller than y; 0 means they are equally large and a positive
  52.    * value means that y is larger than x.
  53.    * 
  54.    * @param {T} x
  55.    * @param {T} y
  56.    * @returns {Number} Returns either -1, 0 or 1.
  57.    */
  58.   compare(x, y) {
  59.     throw new Error('Abstract method.');
  60.   };
  61. };
  64. /**
  65.  * @template T
  66.  */
  67. class DefaultComparer extends Comparer {
  68.   /**
  69.    * Uses the instance of the EqualityComparer to determine whether two
  70.    * items are considered to be equal.
  71.    * @inheritDoc
  72.    * 
  73.    * @param {T} x
  74.    * @param {T} y
  75.    * @returns {Number} Returns either -1, 0 or 1.
  76.    */
  77.   compare(x, y) {
  78.     return this.equalityComparer.equals(x, y) ? 0 : (x < y ? -1 : 1);
  79.   };
  80. };
  84. module.exports = Object.freeze({
  85.   Comparer,
  86.   DefaultComparer
  87. });