XMLHttpRequest和類屬性

Question

我有一個類（你好），這個類有foo屬性，這個屬性必須在xhr請求後填充。如何設置foo從XMLHttpRequest以及如何調用afterLoad()？

function Hello(){ 

    this.foo = null; 

    this.process = function(){ 
     var req = new XMLHttpRequest(); 
     req.open('GET', 'http://some.url', true); 
     req.onload = function(){ 
      // How to set Hello.foo in this context? 
      // And how to call Hello.afterLoad() from this context? 
      // this == XMLHttpRequest instance 
     }; 
     req.send(null); 
    } 
    this.afterLoad = function(){ 
     console.log(this.foo); 
     // Some stuff goes here 
    } 
} 

Answer 1

function Hello(){ 

    this.foo = null; 

    this.process = function(){ 
    var _that = this, 
     req = new XMLHttpRequest(); 
    req.open('GET', 'http://some.url', true); 
    req.onload = function(){ 
     // How to set Hello.foo in this context? 
     // And how to call Hello.afterLoad() from this context? 
     // this == XMLHttpRequest instance 
     _that.foo = 'something'; 
     _that.afterLoad(); 
    }; 
    req.send(null); 
    } 
    this.afterLoad = function(){ 
    console.log(this.foo); 
    // Some stuff goes here 
    } 
}