$（'＃id'）。值未定义 [英] $('#id').value is undefined

问题描述

我在尝试检查字段的长度并根据结果设置值时遇到问题。使用firefox与firefox我一直得到错误'elUsername'没有定义。请告诉我我做错了什么。相当新的JQuery。

I am having trouble with trying to check the length of a field and set a value based on the result. Using firebug with firefox I keep getting the error 'elUsername' is not defined. Please tell me what I am doing wrong. Fairly new to JQuery.

$('#usernameInput').blur(function ()
{
    var elUsername = $('#usernameInput').value;
    var elUsernameFeedback = $('#usernameFeedback');
    if (elUsername.length < 5) {
        elUsernameFeedback.text("Please enter your username");
    }
});

基本上当用户离开该字段并且用户名小于5（仅用于测试）时设置为它的文本提示用户更正错误。但是从不输入if语句。任何帮助将不胜感激。

Basically when the user leaves the field and the username is less than 5 (just for testing) the gets the text set to it to prompt the user to correct the mistake. However the if statement is never entered. Any help would be greatly appreciated.

推荐答案

您正在尝试在jQuery对象上使用本机JavaScript属性。使用：

You're trying to use a native JavaScript property on a jQuery object. Use :

var elUsername = $('#usernameInput').val();

或

var elUsername = document.getElementById('usernameInput').value;

或略显不明显，但仍然有效：

or the slightly less obvious, but still valid:

var elUsername = $('#usernameInput')[0].value;
var elUsername = $('#usernameInput').get(0).value;

这篇关于$（'＃id'）。值未定义的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！