index.js
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/*!
* vary
* Copyright(c) 2014 Douglas Christopher Wilson
* MIT Licensed
*/
/**
* Module exports.
*/
module.exports = vary;
module.exports.append = append;
/**
* Variables.
*/
var separators = /[\(\)<>@,;:\\"\/\[\]\?=\{\}\u0020\u0009]/;
/**
* Append a field to a vary header.
*
* @param {String} header
* @param {String|Array} field
* @return {String}
* @api public
*/
function append(header, field) {
if (typeof header !== 'string') {
throw new TypeError('header argument is required');
}
if (!field) {
throw new TypeError('field argument is required');
}
// get fields array
var fields = !Array.isArray(field)
? parse(String(field))
: field;
// assert on invalid fields
for (var i = 0; i < fields.length; i++) {
if (separators.test(fields[i])) {
throw new TypeError('field argument contains an invalid header');
}
}
// existing, unspecified vary
if (header === '*') {
return header;
}
// enumerate current values
var vals = parse(header.toLowerCase());
// unspecified vary
if (fields.indexOf('*') !== -1 || vals.indexOf('*') !== -1) {
return '*';
}
for (var i = 0; i < fields.length; i++) {
field = fields[i].toLowerCase();
// append value (case-preserving)
if (vals.indexOf(field) === -1) {
vals.push(field);
header = header
? header + ', ' + fields[i]
: fields[i];
}
}
return header;
}
/**
* Parse a vary header into an array.
*
* @param {String} header
* @return {Array}
* @api private
*/
function parse(header) {
return header.trim().split(/ *, */);
}
/**
* Mark that a request is varied on a header field.
*
* @param {Object} res
* @param {String|Array} field
* @api public
*/
function vary(res, field) {
if (!res || !res.getHeader || !res.setHeader) {
// quack quack
throw new TypeError('res argument is required');
}
// get existing header
var val = res.getHeader('Vary') || ''
var header = Array.isArray(val)
? val.join(', ')
: String(val);
// set new header
res.setHeader('Vary', append(header, field));
}