xmpp.chapril.org-conversejs/src/polyfill.js

if (!String.prototype.endsWith) {
  String.prototype.endsWith = function(searchString, position) {
      var subjectString = this.toString();
      if (position === undefined || position > subjectString.length) {
          position = subjectString.length;
      }
      position -= searchString.length;
      var lastIndex = subjectString.indexOf(searchString, position);
      return lastIndex !== -1 && lastIndex === position;
  };
}

String.prototype.splitOnce = function (delimiter) {
    var components = this.split(delimiter);
    return [components.shift(), components.join(delimiter)];
};

if (!String.prototype.trim) {
    String.prototype.trim = function () {
        return this.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, '');
    };
}