undefined

问题 I'm creating a namespace in javascript to loop through a form and create an object. The goal of the function when called is to loop through all of a certain form type and construct an object that has a key which is the html input's name and the value as its current value. However, it keeps returning undefined. Any help would be greatly appreciated: get_form_data.radio = function(container) { //will return the value var data = {}; //function data object to return container.find('input[type=

问题 I'm creating a namespace in javascript to loop through a form and create an object. The goal of the function when called is to loop through all of a certain form type and construct an object that has a key which is the html input's name and the value as its current value. However, it keeps returning undefined. Any help would be greatly appreciated: get_form_data.radio = function(container) { //will return the value var data = {}; //function data object to return container.find('input[type=

问题 I simply want to print the amount of connected MIDI inputs. What in the world am I doing wrong? Using Code::Blocks and GNU GCC Compiler. #include <windows.h> #include <mmsystem.h> #include <stdio.h> int main() { printf("%d", midiInGetNumDevs()); return 0; } I get undefined reference to `midiInGetNumDevs@0' upon compiling. midiInGetNumDevs 回答1: You need to link with with winmm.lib . In Visual Studio, you do this by adding it to the Additional Dependencies in your project properties. Right

问题 I am trying to organize my js file and followed a suggested module pattern. When I use "use-strict" in this pattern a function is declared as undefined, without the "use-strict" method the function just works fine. Is the strict-mode recommended and when yes, why does the function not work with the use of it? var envy = (function( $ ) { 'use strict'; /** * Viewport adjusments. * * @since 1.0.0 */ irp_viewportadjst = function() { $('meta[name="viewport"]').attr('content', 'width=device-width,

问题 Alright this is what my code looks like index.php require_once($WebsiteRoot . "/include/testfile.php"); TestFunction(); /include/testfile.php function TestFunction() { echo "It Works"; } And it gives me the error: Fatal error: Call to undefined function TestFunction() in /path/index.php on line 49 Any idea what i'm doing wrong? Thanks 回答1: Make sure you're including the file you think you are. If your index.php page looks exactly like you've stated, then it won't return anything. If you want

问题 As you seen in this picture below, for some reason my DirectCast wont except ANYTHING for the second argument. It says it requires a type, but, it won't take any object at all! Thanks for any help! I'm using VB.net so all .net answers are acceptable :) EDIT Ok, so apparently I'm not giving it the right kind of type . Could somebody please clarify this? Assuming the type it needs to cast to is gridElement , what should I replace objType with? 回答1: DirectCast requires an object prototype (i.e.

问题 So I'm trying to use React Native's FlatList renderItem property, but something very strange is happening. The data property is set to an array which has elements which are not undefined, but then, in the renderItem function, it gives me an error saying that the argument of the function is undefined, unless I call the argument item . Here's my code: export default class Profile extends React.Component { onLearnMore = (user) => { this.props.navigation.navigate('UserDetail', user) } render() {

问题 I have a function which returns results (or not). The problem is when it does not return any value I get in the console the message cannot read property 'done' of undefined Which is true and I do understand the problem. Also, this error doesn't make my code stop working, but I would like to know if there's any chance of avoiding this? The function in ajax is: function getDelivery(){ var items = new Array(); $("#tab-delivery tr").each(function(){ items.push({"id" : $(this).find('.form-control'

问题 It appears that window.undefined is writable, i.e. it can be set to something else than its default value (which is, unsurprisingly, undefined ). The point is however that whenever I refer to undefined , it refers to window.undefined (as window can be removed in cases like this). So how do I actually get access to an undefined 'instance', so to say? How would I be able to set another variable to undefined , if window.undefined has been changed? If I code: window.undefined = 'foo'; // This

问题 While viewing jQuery's uncompressed source code I stumbled upon something I don't quite understand. When the create their anonymous function, they place undefined as a 2nd argument. What is this doing, and why are they using undefined? Is it necessary to put undefined as an argument in an anonymous function? Below is an example of what I am talking about. (function( window, undefined) { ...code here })( window ); 回答1: What this is doing, is reassigning undefined to undefined inside that