[英]Node.js and undefined properties
I'm trying to use GET variables to transfer some simple data but for some reason I'm doing it wrong. 我正在尝试使用GET变量来传输一些简单的数据,但由于某种原因,我做错了。
My code is pretty simple. 我的代码非常简单。 I use Node.js HTTP & URL libraries. 我使用Node.js HTTP和URL库。 When I try to run following code, I get TypeError: Cannot read property 'foo' of undefined. 当我尝试运行以下代码时,我得到TypeError:无法读取未定义的属性'foo'。 I really don't understand why because foo is passed in the URL and if I do console.log to q object, there's foo value. 我真的不明白为什么因为foo是在URL中传递的,如果我将console.log作为q对象,那就有foo值。
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'})
var vars = url.parse(req.url,true)
var q = vars.query
if(q.foo) {
res.end('yay')
} else res.end('snif')
}).listen(8000,"127.0.0.1")
Your problem is not that foo
doesn't exist, the problem is that q
itself is undefined
. 你的问题不是foo
不存在,问题是q
本身是undefined
。
Where does that come from? 它来自哪里? Well if we clean it up and add some logs... 好吧,如果我们清理它并添加一些日志......
var http = require('http');
var url = require('url');
http.createServer(function (req, res) {
console.log(req.url);
res.writeHead(200, {'Content-Type': 'text/plain'});
var vars = url.parse(req.url, true);
var q = vars.query;
if(q && q.foo) { // this time check that q has a value (or better check that q is an object)
res.end('yay');
} else {
res.end('snif');
}
}).listen(8000,"127.0.0.1");
..we find out that the browser requests: ..我们发现浏览器要求:
/bla?foo=1
/favicon.ico
There you go! 你去! Of course the favicon request has not GET
params, you simply need to check that q
is not undefined
. 当然,favicon请求没有GET
参数,你只需要检查q
是不是undefined
。
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