scripts/node_modules/on-headers/index.js

133 lines
2.6 KiB
JavaScript

/*!
* on-headers
* Copyright(c) 2014 Douglas Christopher Wilson
* MIT Licensed
*/
'use strict'
/**
* Module exports.
* @public
*/
module.exports = onHeaders
/**
* Create a replacement writeHead method.
*
* @param {function} prevWriteHead
* @param {function} listener
* @private
*/
function createWriteHead (prevWriteHead, listener) {
var fired = false
// return function with core name and argument list
return function writeHead (statusCode) {
// set headers from arguments
var args = setWriteHeadHeaders.apply(this, arguments)
// fire listener
if (!fired) {
fired = true
listener.call(this)
// pass-along an updated status code
if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
args[0] = this.statusCode
args.length = 1
}
}
return prevWriteHead.apply(this, args)
}
}
/**
* Execute a listener when a response is about to write headers.
*
* @param {object} res
* @return {function} listener
* @public
*/
function onHeaders (res, listener) {
if (!res) {
throw new TypeError('argument res is required')
}
if (typeof listener !== 'function') {
throw new TypeError('argument listener must be a function')
}
res.writeHead = createWriteHead(res.writeHead, listener)
}
/**
* Set headers contained in array on the response object.
*
* @param {object} res
* @param {array} headers
* @private
*/
function setHeadersFromArray (res, headers) {
for (var i = 0; i < headers.length; i++) {
res.setHeader(headers[i][0], headers[i][1])
}
}
/**
* Set headers contained in object on the response object.
*
* @param {object} res
* @param {object} headers
* @private
*/
function setHeadersFromObject (res, headers) {
var keys = Object.keys(headers)
for (var i = 0; i < keys.length; i++) {
var k = keys[i]
if (k) res.setHeader(k, headers[k])
}
}
/**
* Set headers and other properties on the response object.
*
* @param {number} statusCode
* @private
*/
function setWriteHeadHeaders (statusCode) {
var length = arguments.length
var headerIndex = length > 1 && typeof arguments[1] === 'string'
? 2
: 1
var headers = length >= headerIndex + 1
? arguments[headerIndex]
: undefined
this.statusCode = statusCode
if (Array.isArray(headers)) {
// handle array case
setHeadersFromArray(this, headers)
} else if (headers) {
// handle object case
setHeadersFromObject(this, headers)
}
// copy leading arguments
var args = new Array(Math.min(length, headerIndex))
for (var i = 0; i < args.length; i++) {
args[i] = arguments[i]
}
return args
}