mime-lite/src/Mime.js

Standard mime types for JavaScript

'use strict';

function Mime() {
  this._types = Object.create(null);
  this._extensions = Object.create(null);

  for (let i = 0; i < arguments.length; i++) {
    this.define(arguments[i]);
  }

  this.define = this.define.bind(this);
  this.getType = this.getType.bind(this);
  this.getExtension = this.getExtension.bind(this);
}

Mime.prototype.define = function(typeMap, force) {
  for (let type in typeMap) {
    let extensions = typeMap[type].map(function(t) {
      return t.toLowerCase();
    });
    type = type.toLowerCase();

    for (let i = 0; i < extensions.length; i++) {
      const ext = extensions[i];

      // '*' prefix = not the preferred type for this extension.  So fixup the
      // extension, and skip it.
      if (ext[0] === '*') {
        continue;
      }

      if (!force && (ext in this._types)) {
        throw new Error(
          'Attempt to change mapping for "' + ext +
          '" extension from "' + this._types[ext] + '" to "' + type +
          '". Pass `force=true` to allow this, otherwise remove "' + ext +
          '" from the list of extensions for "' + type + '".'
        );
      }

      this._types[ext] = type;
    }

    // Use first extension as default
    if (force || !this._extensions[type]) {
      const ext = extensions[0];
      this._extensions[type] = (ext[0] !== '*') ? ext : ext.substr(1);
    }
  }
};

Mime.prototype.getType = function(path) {
  path = String(path);
  let last = path.replace(/^.*[/\\]/, '').toLowerCase();
  let ext = last.replace(/^.*\./, '').toLowerCase();

  let hasPath = last.length < path.length;
  let hasDot = ext.length < last.length - 1;

  return (hasDot || !hasPath) && this._types[ext] || null;
};

Mime.prototype.getExtension = function(type) {
  type = /^\s*([^;\s]*)/.test(type) && RegExp.$1;
  return type && this._extensions[type.toLowerCase()] || null;
};

module.exports = Mime;