Ajax

你最好使用Prototype或jQuery这样的库。

Ajax

你最好使用Prototype或jQuery这样的库。

我不熟悉Mac OS的Dashcode小部件，但如果他们让你使用JavaScript库和支持xmlhttprequest，我会使用jQuery，做这样的事情:

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

在纯javascript和返回一个承诺:

  httpRequest = (url, method = 'GET') => {
    return new Promise((resolve, reject) => {
      const xhr = new XMLHttpRequest();
      xhr.open(method, url);
      xhr.onload = () => {
        if (xhr.status === 200) { resolve(xhr.responseText); }
        else { reject(new Error(xhr.responseText)); }
      };
      xhr.send();
    });
  }

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();

// Create a request variable and assign a new XMLHttpRequest object to it.
var request = new XMLHttpRequest()

// Open a new connection, using the GET request on the URL endpoint
request.open('GET', 'restUrl', true)

request.onload = function () {
  // Begin accessing JSON data here
}

// Send request
request.send()