3 * Copyright(c) 2014 Douglas Christopher Wilson
14 module.exports = onHeaders
17 * Create a replacement writeHead method.
19 * @param {function} prevWriteHead
20 * @param {function} listener
24 function createWriteHead (prevWriteHead, listener) {
27 // return function with core name and argument list
28 return function writeHead (statusCode) {
29 // set headers from arguments
30 var args = setWriteHeadHeaders.apply(this, arguments)
37 // pass-along an updated status code
38 if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
39 args[0] = this.statusCode
44 return prevWriteHead.apply(this, args)
49 * Execute a listener when a response is about to write headers.
52 * @return {function} listener
56 function onHeaders (res, listener) {
58 throw new TypeError('argument res is required')
61 if (typeof listener !== 'function') {
62 throw new TypeError('argument listener must be a function')
65 res.writeHead = createWriteHead(res.writeHead, listener)
69 * Set headers contained in array on the response object.
72 * @param {array} headers
76 function setHeadersFromArray (res, headers) {
77 for (var i = 0; i < headers.length; i++) {
78 res.setHeader(headers[i][0], headers[i][1])
83 * Set headers contained in object on the response object.
86 * @param {object} headers
90 function setHeadersFromObject (res, headers) {
91 var keys = Object.keys(headers)
92 for (var i = 0; i < keys.length; i++) {
94 if (k) res.setHeader(k, headers[k])
99 * Set headers and other properties on the response object.
101 * @param {number} statusCode
105 function setWriteHeadHeaders (statusCode) {
106 var length = arguments.length
107 var headerIndex = length > 1 && typeof arguments[1] === 'string'
111 var headers = length >= headerIndex + 1
112 ? arguments[headerIndex]
115 this.statusCode = statusCode
117 if (Array.isArray(headers)) {
119 setHeadersFromArray(this, headers)
120 } else if (headers) {
121 // handle object case
122 setHeadersFromObject(this, headers)
125 // copy leading arguments
126 var args = new Array(Math.min(length, headerIndex))
127 for (var i = 0; i < args.length; i++) {
128 args[i] = arguments[i]