它就像事件,在被刪除之前繫結回撥就觸發一次。
object.once(event, callback function, [context])
<!DOCTYPE html> <head> <title>Event Once Example</title> <script src="https://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" type="text/javascript"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" type="text/javascript"></script> </head> <body> <script type="text/javascript"> //The created object 'myVal' is extended using Backbone.Events method var myVal = _.extend({name:'YiiBai!!!'}, Backbone.Events); //The once() method causes the bound callback to only fire once before being removed myVal.once('hello', function () { document.write("The value after firing once is: "); document.write(this.name);//name will get displayed by referring the current object }); //It triggers the 'hello' event on object 'myVal' myVal.trigger('hello'); </script> </body> </html>
讓我們進行以下步驟來看看上面的程式碼工作:
儲存上述程式碼在檔案once.html
在瀏覽器中開啟這個HTML檔案。