JavaScript中的HTTP GET请求？

我需要在JavaScript中执行HTTP GET请求.最好的方法是什么？

我需要在Mac OS X dashcode小部件中执行此操作.

您可以通过javascript使用托管环境提供的功能:

function httpGet(theUrl)
{
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.open( "GET", theUrl, false ); // false for synchronous request
    xmlHttp.send( null );
    return xmlHttp.responseText;
}

但是,不建议使用同步请求,因此您可能希望使用此命令:

function httpGetAsync(theUrl, callback)
{
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.onreadystatechange = function() { 
        if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
            callback(xmlHttp.responseText);
    }
    xmlHttp.open("GET", theUrl, true); // true for asynchronous 
    xmlHttp.send(null);
}

注意:从Gecko 30.0(Firefox 30.0/Thunderbird 30.0/SeaMonkey 2.27)开始,由于对用户体验的负面影响,主线程上的同步请求已被弃用.

在jQuery中:

$.get(
    "somepage.php",
    {paramOne : 1, paramX : 'abc'},
    function(data) {
       alert('page content: ' + data);
    }
);

上面有很多很棒的建议,但不是很容易重复使用,而且经常充斥着DOM废话和其他隐藏简单代码的漏洞.

这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,但这对我们有用.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
});

新的window.fetchAPI是一个更清洁的替代品XMLHttpRequest,使用ES6承诺.有一个很好的解释在这里,但它归结为(文章):

fetch(url).then(function(response) {
  return response.json();
}).then(function(data) {
  console.log(data);
}).catch(function() {
  console.log("Booo");
});

浏览器支持现在在最新版本中很好(适用于Chrome,Firefox,Edge(v14),Safari(v10.1),Opera,Safari iOS(v10.3),Android浏览器和Android版Chrome),但IE将可能没有获得官方支持.GitHub有一个polyfill可用,建议支持仍在使用中的旧浏览器(特别是2017年3月的Safari和同期的移动浏览器).

我想这是否比jQuery或XMLHttpRequest更方便取决于项目的性质.

这是规范https://fetch.spec.whatwg.org/的链接

编辑:

使用ES7 async/await,这变得简单(基于此Gist):

async function fetchAsync (url) {
  let response = await fetch(url);
  let data = await response.json();
  return data;
}

没有回调的版本

var i = document.createElement("img");
i.src = "/your/GET/url?params=here";

以下是使用JavaScript直接执行此操作的代码.但是,如前所述,使用JavaScript库会更好.我最喜欢的是jQuery.

在下面的例子中,正在调用ASPX页面(作为穷人的REST服务进行服务)以返回JavaScript JSON对象.

var xmlHttp = null;

function GetCustomerInfo()
{
    var CustomerNumber = document.getElementById( "TextBoxCustomerNumber" ).value;
    var Url = "GetCustomerInfoAsJson.aspx?number=" + CustomerNumber;

    xmlHttp = new XMLHttpRequest(); 
    xmlHttp.onreadystatechange = ProcessRequest;
    xmlHttp.open( "GET", Url, true );
    xmlHttp.send( null );
}

function ProcessRequest() 
{
    if ( xmlHttp.readyState == 4 && xmlHttp.status == 200 ) 
    {
        if ( xmlHttp.responseText == "Not found" ) 
        {
            document.getElementById( "TextBoxCustomerName"    ).value = "Not found";
            document.getElementById( "TextBoxCustomerAddress" ).value = "";
        }
        else
        {
            var info = eval ( "(" + xmlHttp.responseText + ")" );

            // No parsing necessary with JSON!        
            document.getElementById( "TextBoxCustomerName"    ).value = info.jsonData[ 0 ].cmname;
            document.getElementById( "TextBoxCustomerAddress" ).value = info.jsonData[ 0 ].cmaddr1;
        }                    
    }
}

复制粘贴就绪版本

//Option with catch
fetch( textURL )
   .then(async r=> console.log(await r.text()))
   .catch(e=>console.error('Boo...' + e));

//No fear...
(async () =>
    console.log(
            (await (await fetch( jsonURL )).json())
            )
)();

短而纯:

const http = new XMLHttpRequest()

http.open("GET", "https://api.lyrics.ovh/v1/toto/africa")
http.send()

http.onload = () => console.log(http.responseText)

var sURL = '/your/url.html?' + (new Date()).getTime();

new Ajax.Request( '/myurl', {
  method:  'get',
  parameters:  { 'param1': 'value1'},
  onSuccess:  function(response){
    alert(response.responseText);
  },
  onFailure:  function(){
    alert('ERROR');
  }
});

var page_content;
$.get( "somepage.php", function(data){
    page_content = data;
});

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);
            }
        }
    };
}

//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();

$http.get('/someUrl').
  success(function(data, status, headers, config) {
    // this callback will be called asynchronously
    // when the response is available
  }).
  error(function(data, status, headers, config) {
    // called asynchronously if an error occurs
    // or server returns response with an error status.
  });