Does 'this' refer to the element that call

问题:

In the snippet below I use $(this) to refer to the element in which the function is being called from. I know it is not correct because I printed out the values and it gave me 'undefined'. How do I refer to the input element?

$(function() {
    $( ".datepicker" ).datepicker({
        onSelect: function (date, obj){
                if(confirm('Is this correct?: '+ date )) {
                    $.post('edit.php', {
                        "row": $(this).data('id'),
                        "date":date,
                        "field":$(this).name,
                        "ajax":'true'
                        });
                    }
                }
    });
});

Here is the html element:

<input 
name="appvAcadVp" 
data-id="someid"  
class="datepicker" size="10" 
type="text"
placeholder="someholder"
>

回答1:

jQuery sets this itself, generally to point to the current element.

Otherwise, in JavaScript...

As a function assigned to a propety

var a = {
   b: function() {
      // `this` is `a`
   }
}

a.b();

Except, where the property becomes assigned to a variable. Observe...

var c = a.b;
c(); // the `this` will point to `window`

---

As a function assigned to a variable

var a = function() {
   // `this` is `window`
}

a();

---

As a Constructor

var C = function() {
   // `this` is `c`
}

var c = new C();

Note that if your forgot to instantiate with new, JavaScript will assign those properties to the global object (window in a browser).

---

In the global scope

// In global scope `this` is `window`
var d = this;

---

As called with call() or apply()

You can also set this explicitly with call() and apply() function methods.

---

Now, to your problem...

Thanks for the explanation of 'this' but I still dont understand why the reference isn't working in my code

My apologies.

$(this).name won't work as this is now a jQuery object and has only a few properties (none of which are name).

Either use $(this).attr('name') or drop wrapping this with the jQuery object and just access this.name.

回答2:

That's what the obj parameter is for in the onSelect function, so you'd reference $(obj). Just for reference, this will refer to the associated input field.

For reference, see: http://jqueryui.com/demos/datepicker/ > Events > onSelect