一种支持旧浏览器的解决方案:

function httpRequest() {
    var ajax = null,
        response = null,
        self = this;

    this.method = null;
    this.url = null;
    this.async = true;
    this.data = null;

    this.send = function() {
        ajax.open(this.method, this.url, this.asnyc);
        ajax.send(this.data);
    };

    if(window.XMLHttpRequest) {
        ajax = new XMLHttpRequest();
    }
    else if(window.ActiveXObject) {
        try {
            ajax = new ActiveXObject("Msxml2.XMLHTTP.6.0");
        }
        catch(e) {
            try {
                ajax = new ActiveXObject("Msxml2.XMLHTTP.3.0");
            }
            catch(error) {
                self.fail("not supported");
            }
        }
    }

    if(ajax == null) {
        return false;
    }

    ajax.onreadystatechange = function() {
        if(this.readyState == 4) {
            if(this.status == 200) {
                self.success(this.responseText);
            }
            else {
                self.fail(this.status + " - " + this.statusText);
            }
        }
    };
}

这段代码可能有点过分，但绝对是安全的。

用法:

//create request with its porperties
var request = new httpRequest();
request.method = "GET";
request.url = "https://example.com/api?parameter=value";

//create callback for success containing the response
request.success = function(response) {
    console.log(response);
};

//and a fail callback containing the error
request.fail = function(error) {
    console.log(error);
};

//and finally send it away
request.send();

你也可以用纯JS来做:

// Create the XHR object.
function createCORSRequest(method, url) {
  var xhr = new XMLHttpRequest();
if ("withCredentials" in xhr) {
// XHR for Chrome/Firefox/Opera/Safari.
xhr.open(method, url, true);
} else if (typeof XDomainRequest != "undefined") {
// XDomainRequest for IE.
xhr = new XDomainRequest();
xhr.open(method, url);
} else {
// CORS not supported.
xhr = null;
}
return xhr;
}

// Make the actual CORS request.
function makeCorsRequest() {
 // This is a sample server that supports CORS.
 var url = 'http://html5rocks-cors.s3-website-us-east-1.amazonaws.com/index.html';

var xhr = createCORSRequest('GET', url);
if (!xhr) {
alert('CORS not supported');
return;
}

// Response handlers.
xhr.onload = function() {
var text = xhr.responseText;
alert('Response from CORS request to ' + url + ': ' + text);
};

xhr.onerror = function() {
alert('Woops, there was an error making the request.');
};

xhr.send();
}

详见:html5rocks教程

最好的方法是使用AJAX(您可以在Tizag页面上找到一个简单的教程)。原因是你可能使用的任何其他技术都需要更多的代码，它不能保证在不返工的情况下跨浏览器工作，并且需要你通过在帧内打开隐藏页面传递url解析其数据并关闭它们来使用更多的客户端内存。 AJAX是解决这种情况的方法。这就是我两年的javascript重度开发讲的。

上面有很多很好的建议，但不是很可重用，而且经常充满了DOM废话和其他隐藏了简单代码的无用之处。

下面是我们创建的一个可重用且易于使用的Javascript类。目前它只有一个GET方法，但这对我们来说是可行的。添加POST不应该对任何人的技能征税。

var HttpClient = function() {
    this.get = function(aUrl, aCallback) {
        var anHttpRequest = new XMLHttpRequest();
        anHttpRequest.onreadystatechange = function() { 
            if (anHttpRequest.readyState == 4 && anHttpRequest.status == 200)
                aCallback(anHttpRequest.responseText);
        }

        anHttpRequest.open( "GET", aUrl, true );            
        anHttpRequest.send( null );
    }
}

使用它就像:

var client = new HttpClient();
client.get('http://some/thing?with=arguments', function(response) {
    // do something with response
});

Ajax

你最好使用Prototype或jQuery这样的库。

集功能，食谱容易和简单

我准备了一组函数，它们在某种程度上是相似的，但如果你知道如何利用它，就会展示新的功能以及Javascript已经达到的简单性。

---

让一些基本常数

---

let data;
const URLAPI = "https://gorest.co.in/public/v1/users";
function setData(dt) {
    data = dt;
}

---

最简单的

---

// MOST SIMPLE ONE 
function makeRequest1() {       
    fetch(URLAPI)
        .then(response => response.json()).then( json => setData(json))
        .catch(error => console.error(error))
        .finally(() => {
            console.log("Data received 1 --> ", data);
            data = null;
    });
}

---

使用承诺和异步工具的变化

---

// ASYNC FUNCTIONS 
function makeRequest2() { 
    fetch(URLAPI)
        .then(async response => await response.json()).then(async json => await setData(json))
        .catch(error => console.error(error))
        .finally(() => {
            console.log("Data received 2 --> ", data);
            data = null;            
        });
}

function makeRequest3() {    
    fetch(URLAPI)
        .then(async response => await response.json()).then(json => setData(json))
        .catch(error => console.error(error))
        .finally(() => {
            console.log("Data received 3 --> ", data);
            data = null;
        });
}

// Better Promise usages
function makeRequest4() {
    const response = Promise.resolve(fetch(URLAPI).then(response => response.json())).then(json => setData(json) ).finally(()=> {
        console.log("Data received 4 --> ", data);

    })
}

---

一个线性函数的演示!!

---

// ONE LINER STRIKE ASYNC WRAPPER FUNCTION 
async function makeRequest5() {
    console.log("Data received 5 -->", await Promise.resolve(fetch(URLAPI).then(response => response.json().then(json => json ))) );
}

值得一提的是——> @Daniel De León可能是最干净的函数*

(async () =>
    console.log(
            (await (await fetch( URLAPI )).json())
            )
)();

---

上面的答案-> By @tggagne显示了HttpClient API的功能。

使用Fetch也可以实现同样的效果。根据此使用MDN获取展示了如何将INIT作为第二个参数传递，基本上打开了使用经典方法(get, post…)轻松配置API的可能性。

---

// Example POST method implementation:
async function postData(url = '', data = {}) {
  // Default options are marked with *
  const response = await fetch(url, {
    method: 'POST', // *GET, POST, PUT, DELETE, etc.
    mode: 'cors', // no-cors, *cors, same-origin
    cache: 'no-cache', // *default, no-cache, reload, force-cache, only-if-cached
    credentials: 'same-origin', // include, *same-origin, omit
    headers: {
      'Content-Type': 'application/json'
      // 'Content-Type': 'application/x-www-form-urlencoded',
    },
    redirect: 'follow', // manual, *follow, error
    referrerPolicy: 'no-referrer', // no-referrer, *no-referrer-when-downgrade, origin, origin-when-cross-origin, same-origin, strict-origin, strict-origin-when-cross-origin, unsafe-url
    body: JSON.stringify(data) // body data type must match "Content-Type" header
  });
  return response.json(); // parses JSON response into native JavaScript objects
}

postData('https://example.com/answer', { answer: 42 })
  .then(data => {
    console.log(data); // JSON data parsed by `data.json()` call
  });

Node

在节点(服务器端)上无法获取

最简单的解决方案(2021年底)是使用Axios。

$ npm install axios

然后运行:

const axios = require('axios');
const request = async (url) => await (await axios.get( url ));
let response = request(URL).then(resp => console.log(resp.data));