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<!DOCTYPE html> <html> <body> <h1>JavaScript Promise</h1> <p>等待 3 秒（3000 毫秒）让此页面发生变化。</p> <h1 id="demo"></h1> <script> const myPromise = new Promise(function(myResolve, myReject) { setTimeout(function(){ myResolve("I love You !!"); }, 3000); }); myPromise.then(function(value) { document.getElementById("demo").innerHTML = value; }); </script> </body> </html>