rollbar/src/utility/headers.js

Effortlessly track and debug errors in your JavaScript applications with Rollbar. This package includes advanced error tracking features and an intuitive interface to help you identify and fix issues more quickly.

import { hasOwn } from '../utility.js';

/*
 * headers - Detect when fetch Headers are undefined and use a partial polyfill.
 *
 * A full polyfill is not used in order to keep package size as small as possible.
 * Since this is only used internally and is not added to the window object,
 * the full interface doesn't need to be supported.
 *
 * This implementation is modified from whatwg-fetch:
 * https://github.com/github/fetch
 */
function headers(headers) {
  if (typeof Headers === 'undefined') {
    return new FetchHeaders(headers);
  }

  return new Headers(headers);
}

function normalizeName(name) {
  if (typeof name !== 'string') {
    name = String(name);
  }
  return name.toLowerCase();
}

function normalizeValue(value) {
  if (typeof value !== 'string') {
    value = String(value);
  }
  return value;
}

function iteratorFor(items) {
  var iterator = {
    next: function () {
      var value = items.shift();
      return { done: value === undefined, value: value };
    },
  };

  return iterator;
}

function FetchHeaders(headers) {
  this.map = {};

  if (headers instanceof FetchHeaders) {
    headers.forEach(function (value, name) {
      this.append(name, value);
    }, this);
  } else if (Array.isArray(headers)) {
    headers.forEach(function (header) {
      this.append(header[0], header[1]);
    }, this);
  } else if (headers) {
    Object.getOwnPropertyNames(headers).forEach(function (name) {
      this.append(name, headers[name]);
    }, this);
  }
}

FetchHeaders.prototype.append = function (name, value) {
  name = normalizeName(name);
  value = normalizeValue(value);
  var oldValue = this.map[name];
  this.map[name] = oldValue ? oldValue + ', ' + value : value;
};

FetchHeaders.prototype.get = function (name) {
  name = normalizeName(name);
  return this.has(name) ? this.map[name] : null;
};

FetchHeaders.prototype.has = function (name) {
  return hasOwn(this.map, normalizeName(name));
};

FetchHeaders.prototype.forEach = function (callback, thisArg) {
  for (var name in this.map) {
    if (hasOwn(this.map, name)) {
      callback.call(thisArg, this.map[name], name, this);
    }
  }
};

FetchHeaders.prototype.entries = function () {
  var items = [];
  this.forEach(function (value, name) {
    items.push([name, value]);
  });
  return iteratorFor(items);
};

export default headers;