How to use the material-components-web.linearProgress.MDCLinearProgress function in material-components-web

$postLink() {
    this.usernameField = new textField.MDCTextField(this._$element.find('.mdc-text-field')[0]);
    this.passwordField = new textField.MDCTextField(this._$element.find('.mdc-text-field')[1]);
    this.passwordConfirmField = new textField.MDCTextField(this._$element.find('.mdc-text-field')[2]);
    this.deviceIdField = new textField.MDCTextField(this._$element.find('.mdc-text-field')[3]);
    this.passwordStrengthProgress = new linearProgress.MDCLinearProgress(this._$element.find('.mdc-linear-progress')[0]);
    this.passwordConfirmField.useNativeValidation = false;
  }

$postLink() {
    var elements = this._$element.find('.mdc-text-field');
    for (var i = 0; i < elements.length; i++) {
      if (i === elements.length - 1) {
        this.passwordconfirm = new textField.MDCTextField(elements[i])
      } else {
        new textField.MDCTextField(elements[i]);
      }
    }
    this.passwordStrengthProgress = new linearProgress.MDCLinearProgress(this._$element.find('.mdc-linear-progress')[0]);
    this.snackbar = new snackbar.MDCSnackbar(this._$element.find('.mdc-snackbar')[0]);
  }