1.代码
<!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>AJAX POST 请求</title>
<style>
#result {
width: 200px;
height: 100px;
border: solid 1px #90b;
}
</style>
</head>
<body>
<button>点击发送</button>
<div id="result"></div>
</body>
<script>
const result = document.getElementById("result");
const btn = document.getElementsByTagName("button")[0];
function sendAJAX(url) {
return new Promise((resolve, reject) => {
const xhr = new XMLHttpRequest();
xhr.open("GET", url);
xhr.send();
xhr.onreadystatechange = function () {
if (xhr.readyState === 4) {
if (xhr.status >= 200 && xhr.status < 300) {
resolve(xhr.response);
} else {
reject(xhr.status);
}
}
};
});
}
btn.addEventListener("click", () => {
sendAJAX("https://api.apiopen.top/getJoke").then(
(value) => {
result.innerHTML = value;
},
(reason) => {
console.log(reason);
}
);
});
</script>
</html>
2.代码讲解
function sendAJAX(url) {
return new Promise((resolve, reject) => {
const xhr = new XMLHttpRequest();
xhr.open("GET", url);
xhr.send();
xhr.onreadystatechange = function () {
if (xhr.readyState === 4) {
if (xhr.status >= 200 && xhr.status < 300) {
resolve(xhr.response);
} else {
reject(xhr.status);
}
}
};
});
}
- 自定义一个方法，方法返回一个Promise对象
btn.addEventListener("click", () => {
sendAJAX("https://api.apiopen.top/getJoke").then(
(value) => {
result.innerHTML = value;
},
(reason) => {
console.log(reason);
}
);
});
- 给按钮添加事件监听程序，当点击的时候，使方法返回的Promise执行then方法，并给promise对象赋值箭头函数，成功发送ajax并返回值
3.运行结果
点击后：
