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212 lines
9.6 KiB
JavaScript
212 lines
9.6 KiB
JavaScript
/* jspsych-xab.js
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* Josh de Leeuw
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* updated Oct 2013
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*
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* This plugin runs a single XAB trial, where X is an image presented in isolation, and A and B are choices, with A or B being equal to X.
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* The subject's goal is to identify whether A or B is identical to X.
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*
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* parameters:
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* stimuli: array of arrays. each interior array represents the stimuli for a single trial.
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* each interior array can be two or three elements. if two elements, then the plugin
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* will show the first one as the target (X). if three elements, then the first is X
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* the second is A and the third is B. the second is considered the target and the third
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* is the foil. this is useful if X and A are not identical, but A is still the correct
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* choice (e.g. a categorization experiment where the goal is to pick the item that is
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* in the same category). stimuli can be paths to images, or html strings.
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* left_key: key code for response associated with image on the left side of the screen.
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* right_key: key code for right side
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* timing_x: how long to display X for in ms
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* timing_xab_gap: how long to show a blank screen in between X and AB in ms.
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* timing_ab: how long to show the screen with AB in ms. -1 will display until a response is given.
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* timing_post_trial: how long to show a blank screen after the trial is complete.
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* is_html: must set to TRUE if the stimuli are HTML strings instead of images.
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* prompt: an HTML string to display under the AB stimuli, e.g. to remind the subject which keys to use
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* data: the optional data object
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*
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*/
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(function($) {
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jsPsych.xab = (function() {
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var plugin = {};
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plugin.create = function(params) {
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// the number of trials is determined by how many entries the params.stimuli array has
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var trials = new Array(params.stimuli.length);
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for (var i = 0; i < trials.length; i++) {
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trials[i] = {};
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trials[i].type = "xab";
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trials[i].x_path = params.stimuli[i][0];
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// if there is only a pair of stimuli, then the first is the target and is shown twice.
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// if there is a triplet, then the first is X, the second is the target, and the third is foil (useful for non-exact-match XAB).
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if (params.stimuli[i].length == 2) {
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trials[i].a_path = params.stimuli[i][0];
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trials[i].b_path = params.stimuli[i][1];
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}
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else {
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trials[i].a_path = params.stimuli[i][1];
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trials[i].b_path = params.stimuli[i][2];
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}
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trials[i].left_key = params.left_key || 81; // defaults to 'q'
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trials[i].right_key = params.right_key || 80; // defaults to 'p'
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// timing parameters
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trials[i].timing_x = params.timing_x || 1000; // defaults to 1000msec.
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trials[i].timing_xab_gap = params.timing_xab_gap || 1000; // defaults to 1000msec.
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trials[i].timing_ab = params.timing_ab || -1; // defaults to -1, meaning infinite time on AB. If a positive number is used, then AB will only be displayed for that length.
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trials[i].timing_post_trial = (typeof params.timing_post_trial === 'undefined') ? 1000 : params.timing_post_trial; // defaults to 1000msec.
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// optional parameters
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trials[i].is_html = (typeof params.is_html === 'undefined') ? false : params.is_html;
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trials[i].prompt = (typeof params.prompt === 'undefined') ? "" : params.prompt;
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trials[i].data = (typeof params.data === 'undefined') ? {} : params.data[i];
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}
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return trials;
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};
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var xab_trial_complete = false;
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plugin.trial = function(display_element, block, trial, part) {
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switch (part) {
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// the first part of the trial is to show the X stimulus.
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case 1:
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// reset this variable to false
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xab_trial_complete = false;
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// how we display the content depends on whether the content is
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// HTML code or an image path.
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if (!trial.is_html) {
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display_element.append($('<img>', {
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src: trial.x_path,
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"class": 'jspsych-xab-stimulus'
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}));
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}
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else {
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display_element.append($('<div>', {
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"class": 'jspsych-xab-stimulus',
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html: trial.x_path
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}));
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}
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// start a timer of length trial.timing_x to move to the next part of the trial
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setTimeout(function() {
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plugin.trial(display_element, block, trial, part + 1);
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}, trial.timing_x);
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break;
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// the second part of the trial is the gap between X and AB.
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case 2:
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// remove the x stimulus
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$('.jspsych-xab-stimulus').remove();
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// start timer
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setTimeout(function() {
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plugin.trial(display_element, block, trial, part + 1);
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}, trial.timing_xab_gap);
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break;
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// the third part of the trial is to display A and B, and get the subject's response
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case 3:
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// randomize whether the target is on the left or the right
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var images = [trial.a_path, trial.b_path];
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var target_left = (Math.floor(Math.random() * 2) === 0); // 50% chance target is on left.
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if (!target_left) {
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images = [trial.b_path, trial.a_path];
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}
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// show the options
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if (!trial.is_html) {
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display_element.append($('<img>', {
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"src": images[0],
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"class": 'jspsych-xab-stimulus'
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}));
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display_element.append($('<img>', {
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"src": images[1],
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"class": 'jspsych-xab-stimulus'
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}));
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}
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else {
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display_element.append($('<div>', {
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"class": 'jspsych-xab-stimulus',
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html: images[0]
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}));
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display_element.append($('<div>', {
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"class": 'jspsych-xab-stimulus',
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html: images[1]
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}));
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}
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if (trial.prompt !== "") {
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display_element.append(trial.prompt);
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}
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// start measuring response time
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var startTime = (new Date()).getTime();
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// if timing_ab is > 0, then we hide the stimuli after timing_ab milliseconds
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if (trial.timing_ab > 0) {
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setTimeout(function() {
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if (!xab_trial_complete) {
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$('.jspsych-xab-stimulus').css('visibility', 'hidden');
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}
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}, trial.timing_ab);
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}
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// create the function that triggers when a key is pressed.
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var resp_func = function(e) {
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var flag = false; // true when a valid key is chosen
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var correct = false; // true when the correct response is chosen
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if (e.which == trial.left_key) // 'q' key by default
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{
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flag = true;
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if (target_left) {
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correct = true;
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}
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}
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else if (e.which == trial.right_key) // 'p' key by default
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{
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flag = true;
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if (!target_left) {
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correct = true;
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}
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}
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if (flag) {
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var endTime = (new Date()).getTime();
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var rt = (endTime - startTime);
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// create object to store data from trial
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var trial_data = {
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"trial_type": "xab",
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"trial_index": block.trial_idx,
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"rt": rt,
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"correct": correct,
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"stimulus_x": trial.x_path,
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"stimulus_a": trial.a_path,
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"stimulus_b": trial.b_path,
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"key_press": e.which
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};
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block.writeData($.extend({}, trial_data, trial.data));
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$(document).unbind('keydown', resp_func); // remove response function from keys
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display_element.html(''); // remove all
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xab_trial_complete = true;
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// move on to the next trial after timing_post_trial milliseconds
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if(trial.timing_post_trial > 0) {
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setTimeout(function() {
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block.next();
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}, trial.timing_post_trial);
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} else {
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block.next();
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}
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}
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};
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$(document).keydown(resp_func);
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break;
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}
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};
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return plugin;
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})();
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})(jQuery);
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