[英]How to check the (empty) value of a input type=“date” in Chrome
I want to check if the user entered a date.我想检查用户是否输入了日期。 But I can't figure it out how to do it.
但我无法弄清楚如何做到这一点。
Here's some javascript code what i already got but doesn't work :这是我已经得到但不起作用的一些 javascript 代码:
var valueDate = document.getElementById('Date').value;
if ( valueDate== null || valueDate== '')
{
alert('Date is empty');
return false;
}
And the HTML <input type="date" name="Date" id="Date"/>
Thanks in advance!和 HTML
<input type="date" name="Date" id="Date"/>
提前致谢!
You could check for a falsy value:你可以检查一个假值:
if (!valueDate) {
// ...
}
The falsy values in JavaScript are: JavaScript 中的假值是:
undefined
null
false
""
0
and -0
0
和-0
0n
NaN
Since document.getElementById('Date').value
is always of type string if a value is set, you don't get false positives like 0
being treated like no input, which would be the case if the type was number
.由于
document.getElementById('Date').value
始终是 string 类型,如果设置了值,您不会得到像0
被视为没有输入的误报,如果类型是number
就会出现这种情况。
I would try using Date.parse() if I were you.如果我是你,我会尝试使用 Date.parse()。
var valueDate = document.getElementById('Date').value;
if(!Date.parse(valueDate)){
alert('date is invalid');
}
http://www.w3schools.com/jsref/jsref_parse.asp http://www.w3schools.com/jsref/jsref_parse.asp
I would do this我会这样做
var valueDate = document.getElementById('Date').value;
if (!valueDate) {
alert('date is invalid');
}else{alert('date is valid')}
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