下面的代码演示了如何做到这一点。

var http = new XMLHttpRequest();
var url = 'get_data.php';
var params = 'orem=ipsum&name=binny';
http.open('POST', url, true);

//Send the proper header information along with the request
http.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');

http.onreadystatechange = function() {//Call a function when the state changes.
    if(http.readyState == 4 && http.status == 200) {
        alert(http.responseText);
    }
}
http.send(params);

如果你有/创建一个对象，你可以用下面的代码把它转换成参数，即:

var params = new Object();
params.myparam1 = myval1;
params.myparam2 = myval2;

// Turn the data object into an array of URL-encoded key/value pairs.
let urlEncodedData = "", urlEncodedDataPairs = [], name;
for( name in params ) {
 urlEncodedDataPairs.push(encodeURIComponent(name)+'='+encodeURIComponent(params[name]));
}

var xhr = new XMLHttpRequest();
xhr.open('POST', 'somewhere', true);
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
xhr.onload = function () {
    // do something to response
    console.log(this.responseText);
};
xhr.send('user=person&pwd=password&organization=place&requiredkey=key');

或者如果你可以指望浏览器的支持，你可以使用FormData:

var data = new FormData();
data.append('user', 'person');
data.append('pwd', 'password');
data.append('organization', 'place');
data.append('requiredkey', 'key');

var xhr = new XMLHttpRequest();
xhr.open('POST', 'somewhere', true);
xhr.onload = function () {
    // do something to response
    console.log(this.responseText);
};
xhr.send(data);

下面是一个完整的应用程序json解决方案:

// Input values will be grabbed by ID
<input id="loginEmail" type="text" name="email" placeholder="Email">
<input id="loginPassword" type="password" name="password" placeholder="Password">

// return stops normal action and runs login()
<button onclick="return login()">Submit</button>

<script>
    function login() {
        // Form fields, see IDs above
        const params = {
            email: document.querySelector('#loginEmail').value,
            password: document.querySelector('#loginPassword').value
        }

        const http = new XMLHttpRequest()
        http.open('POST', '/login')
        http.setRequestHeader('Content-type', 'application/json')
        http.send(JSON.stringify(params)) // Make sure to stringify
        http.onload = function() {
            // Do whatever with response
            alert(http.responseText)
        }
    }
</script>

确保你的后端API可以解析JSON。

例如，在Express JS中:

import bodyParser from 'body-parser'
app.use(bodyParser.json())

var util = {
    getAttribute: function (dom, attr) {
        if (dom.getAttribute !== undefined) {
            return dom.getAttribute(attr);
        } else if (dom[attr] !== undefined) {
            return dom[attr];
        } else {
            return null;
        }
    },
    addEvent: function (obj, evtName, func) {
        //Primero revisar attributos si existe o no.
        if (obj.addEventListener) {
            obj.addEventListener(evtName, func, false);

        } else if (obj.attachEvent) {
            obj.attachEvent(evtName, func);
        } else {
            if (this.getAttribute("on" + evtName) !== undefined) {
                obj["on" + evtName] = func;
            } else {
                obj[evtName] = func;
            }

        }

    },
    removeEvent: function (obj, evtName, func) {
        if (obj.removeEventListener) {
            obj.removeEventListener(evtName, func, false);
        } else if (obj.detachEvent) {
            obj.detachEvent(evtName, func);
        } else {
            if (this.getAttribute("on" + evtName) !== undefined) {
                obj["on" + evtName] = null;
            } else {
                obj[evtName] = null;
            }
        }

    },
    getAjaxObject: function () {
        var xhttp = null;
        //XDomainRequest
        if ("XMLHttpRequest" in window) {
            xhttp = new XMLHttpRequest();
        } else {
            // code for IE6, IE5
            xhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        return xhttp;
    }

};

//START CODE HERE.

var xhr = util.getAjaxObject();

var isUpload = (xhr && ('upload' in xhr) && ('onprogress' in xhr.upload));

if (isUpload) {
    util.addEvent(xhr, "progress", xhrEvt.onProgress());
    util.addEvent(xhr, "loadstart", xhrEvt.onLoadStart);
    util.addEvent(xhr, "abort", xhrEvt.onAbort);
}

util.addEvent(xhr, "readystatechange", xhrEvt.ajaxOnReadyState);

var xhrEvt = {
    onProgress: function (e) {
        if (e.lengthComputable) {
            //Loaded bytes.
            var cLoaded = e.loaded;
        }
    },
    onLoadStart: function () {
    },
    onAbort: function () {
    },
    onReadyState: function () {
        var state = xhr.readyState;
        var httpStatus = xhr.status;

        if (state === 4 && httpStatus === 200) {
            //Completed success.
            var data = xhr.responseText;
        }

    }
};
//CONTINUE YOUR CODE HERE.
xhr.open('POST', 'mypage.php', true);
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');


if ('FormData' in window) {
    var formData = new FormData();
    formData.append("user", "aaaaa");
    formData.append("pass", "bbbbb");

    xhr.send(formData);

} else {

    xhr.send("?user=aaaaa&pass=bbbbb");
}

只是为了让专题读者发现这个问题。我发现，只要你有一个给定的路径，接受的答案就可以工作，但如果你让它为空，它将在IE中失败。以下是我想到的:

function post(path, data, callback) {
    "use strict";
    var request = new XMLHttpRequest();

    if (path === "") {
        path = "/";
    }
    request.open('POST', path, true);
    request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
    request.onload = function (d) {
        callback(d.currentTarget.response);
    };
    request.send(serialize(data));
}

你可以这样写:

post("", {orem: ipsum, name: binny}, function (response) {
    console.log(respone);
})

使用现代JavaScript!

我建议你研究一下fetch。它是ES5的对等版本，使用Promises。它可读性更强，也更容易定制。

Const url = "http://example.com"; fetch (url, { 方法:"POST"， body: new FormData(document.getElementById("inputform"))， //——或—— // body: JSON.stringify({ // user: document.getElementById('user').value， / /…… / /}) })( Response => Response .text() // .json()，等等 //与function(response)相同{return response.text();} ) ( HTML => console.log(HTML) ）;

在Node.js中，你需要使用以下方法导入fetch:

const fetch = require("node-fetch");

如果你想同步使用它(不工作在顶级范围):

const json = await fetch(url, optionalOptions)
  .then(response => response.json()) // .text(), etc.
  .catch((e) => {});

更多信息:

Mozilla的文档

我可以使用吗(2020年11月96%)

大卫·沃尔什教程