ionic-framework/js/views/navBar.js

(function(ionic) {
ionic.ui.NavBar = function(opts) {
  this.el = opts.el;

  this._titleEl = this.el.querySelector('.title');
};

ionic.ui.NavBar.prototype = {
  shouldGoBack: function() {},

  setTitle: function(title) {
    if(!this._titleEl) {
      return;
    }
    this._titleEl.innerHTML = title;
  },

  showBackButton: function(shouldShow) {
    var _this = this;

    if(!this._currentBackButton) {
      var back = document.createElement('a');
      back.className = 'button back';
      back.innerHTML = 'Back';

      this._currentBackButton = back;
      this._currentBackButton.onclick = function(event) {
        _this.shouldGoBack && _this.shouldGoBack();
      }
    }

    if(shouldShow && !this._currentBackButton.parentNode) {
      // Prepend the back button
      this.el.insertBefore(this._currentBackButton, this.el.firstChild);
    } else if(!shouldShow && this._currentBackButton.parentNode) {
      // Remove the back button if it's there
      this._currentBackButton.parentNode.removeChild(this._currentBackButton);
    }
  }
};
})(ionic = window.ionic || {});