​x
 
<!DOCTYPE html>
<html>
<body>
​
<h1>JavaScript 布尔</h1>
​
<p>如果布尔值为 true，则显示 "green"，否则显示 "red"。</p>
​
<p id="demo"></p>
​
<script>
Boolean.prototype.myColor = function() {
  if (this.valueOf() == true) {
    return "green";
  } else {
    return "red";
  }
};
​
let a = true;
document.getElementById("demo").innerHTML = a.myColor();
</script>
​
</body>
</html>
​