dc.js

var expr = ['random', 1000, '*', 'round'];

var calc = function (expr) {
  var stack = []
    , left, right;

  for (var i = 0; i < expr.length; i += 1) {
    var val = expr[i];

    console.dir(stack);

    if (!isNaN(val)) {
      stack.push(val);
    } else {
      // 0-ary operators
      if (~['random'].indexOf(val)) {
      // Binary operators
      } else if (~['*','/','+','-'].indexOf(val)) {
        right = stack.pop();
        left = stack.pop();
      // Unary operators
      } else if (~['sqrt', 'round'].indexOf(val)) {
        left = stack.pop();
      }
      switch (val) {
        case 'random': 
          stack.push(Math.random());
          break;
        case '*':
          stack.push(left * right);
          break;
        case '/':
          stack.push(left / right);
          break;
        case '+':
          stack.push(left | 0 + right);
          break;
        case '-':
          stack.push(left - right);
          break;
        case 'sqrt': 
          stack.push(Math.sqrt(left));
          break;
        case 'round':
          stack.push(Math.round(left));
          break;
        
        default:
          console.log('error');
      }
    }
  }
  return stack[0];
};

console.log(calc(expr));