JS Cookie manager for front-end. Without jquery, angular, etc

cookie.js

window.Cookies = {

  /**
   * Get the value of a cookie by its key
   * @param key {String} Cookie's key
   * @param deleteAfter {Boolean} Delete this cookie after reading its value
   */
  read: function ( key, deleteAfter  ){
    var cookies = document.cookie.split( '; ' );
    for ( var i = 0, li = cookies.length; i < li; i++ ) {
      var cookie = cookies[ i ].split( '=' );
      if ( cookie[0] === key ) {
        var val = decodeURIComponent( cookie[1] );
        if ( deleteAfter ) {
          this.erase( key );
        }
        return val;
      }
    }
    return null;
  },

  /**
   * Erase a cookie by its keys
   * @param key {String} Cookie's key
   */
  erase: function ( key ) {
    var date = new Date();
    date.setDate( date.getDate() - 1 );
    document.cookie = key + '=;expires=' + date.toGMTString();
  },

  /**
   * Writes a new cookie
   * @param key {String} The cookie key
   * @param value {Object} A value to be stored, will be stringified
   * @param opts {Object} Other cookie options
   * @param opts.expires {Date} The date to expires the cookie. Default: one year
   * @param opts.expiresInDays {Date} Time to expires the cookie in days
   * @param opts.expiresInYears {Date} Time to expires the cookie in years
   * @param opts.path {Date} The path to save the cookie, default '/'
   */
  write: function ( key, value, opts ) {
    var expires = new Date();
    opts = opts || { };
    if (opts.expires && opts.expires.constructor.name === 'Date') {
      expires = opts.expires;
    } else if ( opts.expiresInDays && opts.expiresInDays.constructor.name === 'Number' ) {
      expires.setDate( expires.getDate() + opts.expiresInDays );
    } else if ( opts.expiresInYears && opts.expiresInYears.constructor.name === 'Number' ) {
      expires.setFullYear( expires.getFullYear() + opts.expiresInYears );
    } else {
      expires.setFullYear( expires.getFullYear() + 1 );
    }
    document.cookie = key + '=' + escape( JSON.stringify( value ) )
      + ';expires=' + expires.toGMTString()
      + ';path=' + ( opts.path ? opts.path : '/' );
  }
};