<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <title>promise 输出 1 2 3</title> </head> <body> <script> const arr = [1, 2, 3]; arr.reduce((p, x) => { return p.then(() => { return new Promise(r => { setTimeout(() => r(console.log(x)), 1000); }); }); }, Promise.resolve()); </script> </body> </html>