同步发送HTTP请求
同步发送HTTP请求，是指在发送请求后，程序会等待服务器响应并接收完整的响应数据后才会继续执行后续代码。
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<head><meta charset="UTF-8"><title>同步请求</title><style>.container{margin: 0 auto;width: 400px;height: 300px;display:flex;flex-direction: column;}</style><script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script>
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<body><div class="container"><div style="flex:1;background-color:coral"><button onclick="asyncAjax1()">Ajax同步请求1，用于判断资源是否存在~</button><br/><button onclick="asyncAjax2()">Ajax同步请求2，直接返回内容~</button><br/><button onclick="asyncFetch()">Fetch同步请求，直接返回内容~</button><br/><button onclick="asyncAxios()">Axios同步请求，直接返回内容~</button></div><div id="output" style="flex:1;background-color: aqua;"></div></div><script type="text/javascript">function asyncAjax1(){console.log('asyncAjax1()');const url = '/index.html';try{var request = new XMLHttpRequest();// false表示同步request.open('GET', url, false);request.send(null);if (request.status === 200) {// return true;document.getElementById('output').innerHTML='success!';} else {// return false;}}catch (e){console.log('错误：',e);// return false;}}asyncAjax2 = () => {console.log('asyncAjax2()');const url = '/api/demo/demo01';let content = '';try{var xhRequest = new XMLHttpRequest();xhRequest.open('POST', url, false);xhRequest.setRequestHeader("Content-Type", "application/json");var data = JSON.stringify({key: "value"});xhRequest.send(data);if (xhRequest.readyState === 4 && xhRequest.status === 200) {content = xhRequest.responseText;} }catch (e){console.log('错误：',e);}document.getElementById('output').innerHTML=content;}asyncFetch = async ()=>{console.log('asyncFetch()');const url = '/api/demo/demo01';let content = '';try{const response = await fetch(url, {method: 'POST', // 或 'GET'headers: {'Content-Type': 'application/json',},body: JSON.stringify({key: 'value'}),});if (!response.ok) {throw new Error(`HTTP error! Status: ${response.status}`);}// console.log(await response.text());content = JSON.stringify(await response.json());}catch(e){console.log('错误：',e);}document.getElementById('output').innerHTML=content;}asyncAxios = async ()=>{console.log('asyncAxios()');const url = '/api/demo/demo01';let content = '';try {const response = await axios.post(url, {key: 'value'});content = JSON.stringify(response.data);} catch (e) {console.log('错误：',e);}document.getElementById('output').innerHTML=content;}</script>
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