<!DOCTYPE html> <html> <body> <h1>JavaScript Set</h1> <p>将变量添加到 Set:</p> <p id="demo"></p> <script> // 创建 Set const letters = new Set(); // 创建变量 const a = "a"; const b = "b"; const c = "c"; // 将变量添加到 Set letters.add(a); letters.add(b); letters.add(c); // Display set.size document.getElementById("demo").innerHTML = letters.size; </script> </body> </html>