jsPsych/plugins/jspsych-instructions.js

/* jspsych-text.js
 * Josh de Leeuw
 *
 * This plugin displays text (including HTML formatted strings) during the experiment.
 * Use it to show instructions, provide performance feedback, etc...
 *
 * documentation: docs.jspsych.org
 *
 *
 */

(function($) {
    jsPsych.instructions = (function() {

        var plugin = {};

        plugin.create = function(params) {

            params = jsPsych.pluginAPI.enforceArray(params, ['pages']);

            var trials = new Array(1);

            trials[0] = {};
            trials[0].pages = params.pages;
            trials[0].key_forward = params.key_forward || 'rightarrow';
            trials[0].key_backward = params.key_backward || 'leftarrow';
            trials[0].allow_backward = (typeof params.allow_backward === 'undefined') ? true : params.allow_backward;
            trials[0].allow_keys = (typeof params.allow_keys === 'undefined') ? true : params.allow_keys;
            trials[0].show_clickable_nav = (typeof params.show_clickable_nav === 'undefined') ? false : params.show_clickable_nav;

            return trials;
        };

        plugin.trial = function(display_element, trial) {

            // if any trial variables are functions
            // this evaluates the function and replaces
            // it with the output of the function
            trial = jsPsych.pluginAPI.evaluateFunctionParameters(trial);

            var current_page = 0;

            var view_history = [];

            var start_time = (new Date()).getTime();

            var last_page_update_time = start_time;

            function show_current_page(){
              display_element.html(trial.pages[current_page]);

              if(trial.show_clickable_nav){

                var nav_html = "<div class='jspsych-instructions-nav'>";
                if(current_page != 0 && trial.allow_backward){
                  nav_html += "<button id='jspsych-instructions-back'>&lt; Previous</button>";
                }
                nav_html += "<button id='jspsych-instructions-next'>Next &gt;</button></div>"

                display_element.append(nav_html);

                if(current_page != 0 && trial.allow_backward){
                  $('#jspsych-instructions-back').on('click',function(){
                    clear_button_handlers();
                    back();
                  });
                }

                $('#jspsych-instructions-next').on('click',function(){
                  clear_button_handlers();
                  next();
                });

              }
            }

            function clear_button_handlers() {
              $('#jspsych-instructions-next').off('click');
              $('#jspsych-instructions-back').off('click');
            }

            function next() {

              add_current_page_to_view_history()

              current_page++;

              // if done, finish up...
              if(current_page >= trial.pages.length) {
                endTrial();
              } else {
                show_current_page();
              }

            }

            function back() {

              add_current_page_to_view_history()

              current_page--;

              show_current_page();
            }

            function add_current_page_to_view_history(){

              var current_time = (new Date()).getTime();

              var page_view_time = current_time - last_page_update_time;

              view_history.push({
                page_index: current_page,
                viewing_time: page_view_time
              });

              last_page_update_time = current_time;
            }

            function endTrial() {

              if(trial.allow_keys){
                jsPsych.pluginAPI.cancelKeyboardResponse(keyboard_listener);
              }

              display_element.html('');

              jsPsych.data.write({
                "view_history": JSON.stringify(view_history),
                "rt": (new Date()).getTime() - start_time
              });

              jsPsych.finishTrial();
            }

            var after_response = function(info) {

                // check if key is forwards or backwards and update page
                if(info.key === trial.key_forward || info.key === jsPsych.pluginAPI.convertKeyCharacterToKeyCode(trial.key_forward)){
                  next();
                }

                if(info.key === trial.key_backward || info.key === jsPsych.pluginAPI.convertKeyCharacterToKeyCode(trial.key_backward)){
                  if(current_page !== 0 && trial.allow_backward) {
                    back();
                  }
                }

                // have to reinitialize this instead of letting it persist to prevent accidental skips of pages by holding down keys too long
                keyboard_listener = jsPsych.pluginAPI.getKeyboardResponse(after_response, [trial.key_forward, trial.key_backward]);
            };

            show_current_page();

            if(trial.allow_keys){
              var keyboard_listener = jsPsych.pluginAPI.getKeyboardResponse(after_response, [trial.key_forward, trial.key_backward]);
            }
        };

        return plugin;
    })();
})(jQuery);