mathjs/lib/chaining/Selector.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser and offers an integrated solution to work with numbers, big numbers, complex numbers, units, and matrices.

module.exports = function (math) {
  var string = require('../util/string');

  /**
   * @constructor Selector
   * Wrap any value in a Selector, allowing to perform chained operations on
   * the value.
   *
   * All methods available in the math.js library can be called upon the selector,
   * and then will be evaluated with the value itself as first argument.
   * The selector can be closed by executing selector.done(), which will return
   * the final value.
   *
   * The Selector has a number of special functions:
   * - done()             Finalize the chained operation and return the
   *                      selectors value.
   * - valueOf()          The same as done()
   * - toString()         Returns a string representation of the selectors value.
   *
   * @param {*} [value]
   */
  function Selector (value) {
    if (!(this instanceof Selector)) {
      throw new SyntaxError('Constructor must be called with the new operator');
    }

    if (value instanceof Selector) {
      this.value = value.value;
    }
    else {
      this.value = value;
    }
  }

  /**
   * Close the selector. Returns the final value.
   * Does the same as method valueOf()
   * @returns {*} value
   */
  Selector.prototype.done = function () {
    return this.value;
  };

  /**
   * Close the selector. Returns the final value.
   * Does the same as method done()
   * @returns {*} value
   */
  Selector.prototype.valueOf = function () {
    return this.value;
  };

  /**
   * Get a string representation of the value in the selector
   * @returns {String}
   */
  Selector.prototype.toString = function () {
    return string.format(this.value);
  };

  /**
   * Create a proxy method for the selector
   * @param {String} name
   * @param {*} value       The value or function to be proxied
   */
  function createProxy(name, value) {
    var slice = Array.prototype.slice;
    if (typeof value === 'function') {
      // a function
      Selector.prototype[name] = function () {
        var args = [this.value].concat(slice.call(arguments, 0));
        return new Selector(value.apply(this, args));
      }
    }
    else {
      // a constant
      Selector.prototype[name] = new Selector(value);
    }
  }

  Selector.createProxy = createProxy;

  /**
   * initialise the Chain prototype with all functions and constants in math
   */
  for (var prop in math) {
    if (math.hasOwnProperty(prop)) {
      createProxy(prop, math[prop]);
    }
  }

  return Selector;
};