Javascript 回调不是函数
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Callback is not a function
提问by Peter
I am trying to retrieve a json object to use it in another module, but I have a problem with callback. I have the error "callback is not a function". I use callback because my variable description is undefined, so i guess it's a problem of asynchronous.
我正在尝试检索一个 json 对象以在另一个模块中使用它，但是我遇到了回调问题。我有错误“回调不是函数”。我使用回调是因为我的变量描述未定义，所以我猜这是异步的问题。
Could you help me plz :)
你能帮我吗 :)
var leboncoin = function () {
var http = require('http')
var bl = require('bl')
http.get("http://www.website.com", function (response, callback) {
response.pipe(bl(function (err, data) {
if (err) {
return console.error(err)
callback(err);
}
var data = data.toString()
var brand = ...
var model = ...
var releaseDate = ...
var km = ...
var fuel = ...
var gearbox = ...
description.Brand = brand;
description.Model = model;
description.Year = releaseDate;
description.KM = km;
description.Fuel = fuel;
description.Gearbox = gearbox;
callback(description);
return (description)
/*console.log(description.Brand);
console.log(description.Model);
console.log(description.Year);
console.log(description.KM);
console.log(description.Fuel);
console.log(description.Gearbox);*/
}))
})
}
exports.leboncoin = leboncoin;
var module = require('./leboncoin');
var res = module.leboncoin();
console.log(res);
回答by
Callbacks aren't magic that just appear. You need to define a parameter to your function and pass the callback you want to use.
回调并不是刚刚出现的魔法。您需要为您的函数定义一个参数并传递您想要使用的回调。
// --------------------------v
var leboncoin = function (callback) {
var http = require('http')
var bl = require('bl')
http.get("http://www.website.com", function (response) {
response.pipe(bl(function (err, data) {
if (err) {
callback(err);
return;
}
var data = data.toString()
var description = { /* your description object */ }
callback(description);
}))
})
}
exports.leboncoin = leboncoin;
var module = require('./leboncoin');
// -----------------vvvvvvvv
module.leboncoin(function(res) {
console.log(res);
});
回答by skypHyman
The method http.getrequires a function that accepts only a parameter named response(or whatever you want, the name doesn't matter indeed), thus your second one, callback, is undefined and invoking it will end ever in that error.
该方法http.get需要一个函数，该函数只接受一个命名参数response（或任何你想要的参数，名称实际上并不重要），因此你的第二个，callback, 是未定义的，调用它会以该错误结束。
