我怎样才能最好地处理以下情况?
我有一个构造函数需要一段时间才能完成.
var Element = function Element(name){
this.name = name;
this.nucleus = {};
this.load_nucleus(name); // This might take a second.
}
var oxygen = new Element('oxygen');
console.log(oxygen.nucleus); // Returns {}, because load_nucleus hasn't finished.
我看到三种 Select ,每一种似乎都不寻常.
One,向构造函数添加回调.
var Element = function Element(name, fn){
this.name = name;
this.nucleus = {};
this.load_nucleus(name, function(){
fn(); // Now continue.
});
}
Element.prototype.load_nucleus(name, fn){
fs.readFile(name+'.json', function(err, data) {
this.nucleus = JSON.parse(data);
fn();
});
}
var oxygen = new Element('oxygen', function(){
console.log(oxygen.nucleus);
});
Two,使用EventEmitter发出"已加载"事件.
var Element = function Element(name){
this.name = name;
this.nucleus = {};
this.load_nucleus(name); // This might take a second.
}
Element.prototype.load_nucleus(name){
var self = this;
fs.readFile(name+'.json', function(err, data) {
self.nucleus = JSON.parse(data);
self.emit('loaded');
});
}
util.inherits(Element, events.EventEmitter);
var oxygen = new Element('oxygen');
oxygen.once('loaded', function(){
console.log(this.nucleus);
});
Or three,阻止建造师.
var Element = function Element(name){
this.name = name;
this.nucleus = {};
this.load_nucleus(name); // This might take a second.
}
Element.prototype.load_nucleus(name, fn){
this.nucleus = JSON.parse(fs.readFileSync(name+'.json'));
}
var oxygen = new Element('oxygen');
console.log(oxygen.nucleus)
但我以前从没见过这样的事.
我还有什么 Select ?