Useful JavaScript Game Extensions: Array#rand

Ayn Rand

Part 3 of 256.

/**
 * Randomly select an element from the array. The array remains unmodified.
 *
 * @returns A random element from an array, or undefined if the array is empty.
 */
Array.prototype.rand = function() {
  return this[rand(this.length)];
};

Building on the last installment of a global rand method, we can easily extend Array to provide simple random element selection.

// Example:
["rock", "paper", "scissors"].rand()

Selecting options from a loot table, or random AI actions is now wonderfully easy. With all these extensions the theme is the same, start with the best interface for the programmer and extend what you must to make it happen.

Useful JavaScript Game Extensions: rand

Rand Atlas Shrugged
Part 2 of my 256 part series: Useful JavaScript Game Extensions!

/**
 * Generate uniformly distributed random numbers.
 *
 * @param {Number} [n]
 * @returns A Random integers from [0, n) if n is given, otherwise a random float
 * between 0 and 1.
 * @type Number
 */
function rand(n) {
  if(n !== undefined) {
    return Math.floor(Math.random() * n);
  } else {
    return Math.random();
  }
}

Some games make use of random numbers… a lot. So when choosing the best interface it is important to keep that in mind. Often times uniform distributions are the way to go, such as when selecting from an array, or rolling a six sided die. If one often has need of a variety of random distributions then having different methods live in a Random namespace would probably be best. For simple, everyday use a little rand(6) is very convenient.

Useful JavaScript Game Extensions: Clamp

Give him the clamps!

Part 1 of my new 256 part series on simple JavaScript extensions to make game programming easy and fun!

/**
 * Returns a number whose value is limited to the given range.
 *
 * Example: limit the output of this computation to between 0 and 255
 * (x * 255).clamp(0, 255)
 *
 * @param {Number} min The lower boundary of the output range
 * @param {Number} max The upper boundary of the output range
 * @returns A number in the range [min, max]
 * @type Number
 */
Number.prototype.clamp = function(min, max) {
  return Math.min(Math.max(this, min), max);
};

Note that this extends the behavior of the Number class. Some may consider it poor form to “mess with” the JS built-ins, but I consider it poor form to expose a worse than necessary interface to the programmer. Compare:

// Namespace?
STRd6.Util.clamp(x * 255, 0, 255);

// global function clamp?
clamp(x * 255, 0, 255);

// Clean, simple and object oriented!
(x * 255).clamp(0, 255);

Stay tuned for the next 255 parts of the series!