progidea.js

function output(x){
  console.log(x);
}

var funcs = [
  function(x,y){return x+y},
  function(x,y){return x-y},
  function(x,y){return x*y},
  function(x,y){return x/y},
  function(x){return x*x},
  function(x){return Math.sqrt(x)},
  function(x){return x+1},
  function(x){return x-1},
  function(x,y){return Math.pow(x,y)},
  function(x,y,z){return x?y:z},
  function(x,y){return Math.pow(x,y)},
  function(x){return String.fromCharCode(x)},
  function(x){return x.charCodeAt()},
  function(){return Math.E},
  function(){return Math.PI},
  function(){return 0},
  function(){return 1},
  function(){return 2},
  function(){return 3},
  function(){return 4},
  function(){return 5},
  function(){return 6},
  function(){return 7},
  function(){return 8},
  function(){return 9},
  function(){return 10},
  function(){return 11},
  function(){return 12},
  function(){return 13},
  function(){return 14},
  function(){return 15},
  function(){return 16},
  function(){return 50},
  function(){return 100},
  function(){return 1000},
  function(x){return new Function("a","b","c","d","e","return "+x)},
  function(x){return eval(x)},
  function(i,f){return this[i]=typeof f==="function"?f:new Function("return "+f)},
  function(){return +prompt()},
  function(){return prompt.charCodeAt()},
  function(x){return [x]},
  function(l){return this.splice(-l)},
  function(l){a=this.splice(-l);this.push.apply(this,a)},
  function(){return this[this.length-1];},
  function(x){output(String.fromCharCode(x))},
  function(x){output(String.fromCharCode(x));return x;}
];

function steps(code){
  code = code.split("").map(function(e){return e.charCodeAt();});
  code = code.slice(0,-1).map(function(e,i){return Math.abs(code[i+1]-e);});
  return code;
}

function parse(code){
  code = steps(code);
  var f = funcs.slice();
  var stack = [];
  code.forEach(function(e){
  //  console.log(stack);
    var fp = f[e];
    var res = fp.apply(f,stack.splice(stack.length-fp.length,fp.length));
    if(typeof res !== "undefined" && res !== null)
      stack.push(res);
  });
  return stack;
}

// suboptimal solution
var nums = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,50,100];
function aval(n){return nums.indexOf(n) >= 0;}
function genNum(n,k){
  k = k || [];
  if(aval(n)){
    k.push(n);
    return k;
  } else if(nums.map(function(e){return n-e;}).some(aval)){
    for(var i=0;i<nums.length;i++)
      if(aval(n-nums[i])){
        k = k.concat(genNum(n-nums[i]));
        k.push(nums[i],"+");
        return k;
      }
  } else if(n > 0){
    for(var i=nums.length;i-->0;)if(n-nums[i]>=0)break;
    k = k.concat(genNum(n-nums[i]));
    k.push(nums[i],"+");
    return k;
  } else return null;
}

// maps a series of instructions to differences
function mp(a){
  return a.map(function(e){
    return aval(e)?nums.indexOf(e)+15:e=="+"?0:-1;
  });
}

// suboptimal generation of source
function subBrute(ins){
  var counter = 33;
  return String.fromCharCode(counter)+ins.map(function(e){
    return String.fromCharCode(counter += e);
  }).join("");
}

function bruteGenString(str){
  str = str.split("");
  return subBrute([].concat.apply([],str.map(function(e){
    return mp(genNum(e.charCodeAt()).concat(44));
  })));
}