jsPattern.prototypeCacheVal.js - cache value with a new Function.prototype method.

jsPattern.prototypeCacheVal.js

Function.prototype.memoized = function (key) {
    this._values = this._values || {};
    return this._values[key] !== undefined ? this._values[key] : this._values[key] = this.apply(this, arguments);
};
Function.prototype.memoize = function () {
    var fn = this;
    return function () {
        return fn.memoized.apply(fn, arguments);
    };
};
var isPrime = (function (num) {
    var prime = num != 1;
    for (var i = 2; i < num; i++) {
        if (num % i === 0) {
            prime = false;
            break;
        }
    }
    return prime;
}).memoize();
assert(isPrime(17), "17 is prime");