Nodejs: fixed the "Can't remove headers after they are sent" exception caused by the cancellation of res. download of express.

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From Baidu?

Presumably, you may have encountered the same problem as me.

In express, if we use res. download to process file downloads and the download is canceled midway through, the following exception will occur:

node.js:116    throw e; // process.nextTick error, or 'error' event on first tick        ^        Error: Can't remove headers after they are sent.        at ServerResponse.removeHeader (http.js:537:11)        at Socket. (/usr/local/lib/node/.npm/express/2.0.0rc/package/lib/response.js:205:19)        at Socket.emit (events.js:59:20)        at Array. (net.js:799:27)        at EventEmitter._tickCallback (node.js:108:2

I checked the source code of express and found that the "Content-Disposition" http header will be removed when err occurs. This will cause exceptions because the response has been sent to the client, we only need to set the "if (err) self. removeHeader ('content-disposition'); "comment out the source code.
If you do not want to modify the source code of express, we can perform a simple fix on express after require ('express:

var express = require('express');//fixed express download cancel bug:require('http').ServerResponse.prototype.download = function(path, filename, fn){    var self = this;    // support callback as second arg     if ('function' == typeof filename) {        fn = filename;        filename = null;    }    // transfer the file     this.attachment(filename || path).sendfile(path, function(err){        // if (err) self.removeHeader('Content-Disposition');         if (fn) return fn(err);        if (err) {            self.req.next('ENOENT' == err.code                ? null                : err);        }    });};

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^_^. I hope this article will be useful to you.