[英]How to get the result inside callback function in javascript?
如果我想将结果写入回调函数中以进行响应,但是我无法访问该函数中的res变量,也无法访问该函数之外的结果。
那么如何在内部和外部之间传递价值呢?
var http = require('http');
var url = require('url');
http.createServer
(
function (req, res)
{
var output='';
res.writeHead(200, {'Content-Type': 'text/plain'});
//The url we want is: 'www.random.org/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
var options = {
host: 'www.random.org',
path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
callback = function(response) {
var str = '';
//another chunk of data has been recieved, so append it to `str`
response.on('data', function (chunk) {
str += chunk;
});
//the whole response has been recieved, so we just print it out here
response.on('end', function () {
console.log(str);
//output+=str; //get result
});
}
http.request(options, callback).end();
//output+=str; //get result
res.end(output);
}
).listen(80, '127.0.0.1');
版本2
var http = require('http');
var url = require('url');
http.createServer
(
function (req, res)
{
var output='';
res.writeHead(200, {'Content-Type': 'text/plain'});
//The url we want is: 'www.random.org/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
var options = {
host: 'www.random.org',
path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
callback = function(response) {
var str = '';
//another chunk of data has been recieved, so append it to `str`
response.on('data', function (chunk) {
str += chunk;
});
//the whole response has been recieved, so we just print it out here
response.on('end', function () {
res.write('inside');
});
}
http.request(options, callback).end();
res.write('outside');
res.end(output);
}
).listen(80, '127.0.0.1');
版本3
var http = require('http');
var url = require('url');
http.createServer
(
function (req, res)
{
res.writeHead(200, {'Content-Type': 'text/plain'});
//The url we want is: 'www.random.org/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
var options = {
host: 'www.random.org',
path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
callback = function(res) {
var str = '';
//another chunk of data has been recieved, so append it to `str`
res.on('data', function (chunk) {
str += chunk;
});
//the whole response has been recieved, so we just print it out here
res.on('end', function () {
res.write('inside');
//or
this.write('inside');
});
}
http.request(options, callback).end();
res.write('outside');
res.end();
}
).listen(80, '127.0.0.1');
版本4
var http = require('http');
var url = require('url');
http.createServer
(
function (req, res)
{
res.writeHead(200, {'Content-Type': 'text/plain'});
//The url we want is: 'www.random.org/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
var options = {
host: 'www.random.org',
path: '/integers/?num=1&min=1&max=10&col=1&base=10&format=plain&rnd=new'
};
callback = function(response) {
var str = '';
//another chunk of data has been recieved, so append it to `str`
response.on('data', function (chunk) {
str += chunk;
});
//the whole response has been recieved, so we just print it out here
response.on('end', function () {
res.write('inside');
});
}
http.request(options, callback);
res.write('outside');
res.end();
}
).listen(80, '127.0.0.1');
你不能 设置回调的函数将在回调执行之前完成并返回。 如果没有,则不需要回调。
在回调本身(而不是父函数)中执行您需要做的所有工作。
我无法访问函数中的res变量
你应该能够。 它仍然在范围内。
(尽管如果您在回调运行之前在其上调用end()
,则应该预期会损坏)。
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