​x
 
<html>
<body>
​
<script type="text/javascript">
​
Function.prototype.originalToString = Function.prototype.toString;
​
Function.prototype.toString = function() {
  if (this.originalToString().length > 100) {
    return "Function too long to display.";
  } else {
    return this.originalToString();
  }
};
​
function sayHi() {
  alert("hi");
}
​
document.write(sayHi.toString());
​
</script>
​
</body>
</html>
​