使用jQuery判断文件输入字段是否为空

Question

I have a PHP form with a file input field, and two text input fields. What I want to do is use jQuery to check if the file input field is empty, and if it's not, then show a specific div, but the following code does not work:

<input type="file" name="blog-entry-image" id="blog-entry-image" />

var fileInput = $.trim($("#blog-entry-image").val());
if (fileInput.length > 0) {
        $("#new-blogentry").click(function() {
        $("#sending").show();
        return true;
    }); 
}

"new-blogentry" is the submit button, and "sending" is a div with an animated gif.

Answer 1

<input type="file" name="blog-entry-image" id="blog-entry-image" />

$(document).ready(function (){
    $("#blog-entry").click(function() {
        var fileInput = $.trim($("#blog-entry-image").val());
        if (fileInput && fileInput !== '') {      
                $("#sending").show();
                return true;    
        }
  });
});