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82 lines
2.6 KiB
Markdown
82 lines
2.6 KiB
Markdown
# Event-related callback functions
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jsPsych offers the ability to call arbitrary functions in response to certain events occuring, like the end of a trial or when new data is saved. This page summarizes the different opportunities for callback functions and how to specify them.
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---
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## on_data_update
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The `on_data_update` callback can be declared in the `jsPsych.init` method. The callback triggers whenever data is generated by a plugin (specifically, whenever the `jsPsych.data.write` method is called). The function will be passed a single argument, which contains the data that was written.
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#### Sample use
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```javascript
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jsPsych.init({
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experiment_structure: exp,
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on_data_update: function(data) {
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console.log('Just added new data. The contents of the data are: '+JSON.stringify(data));
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}
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});
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```
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---
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## on_finish (trial)
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The `on_finish` callback can be added to any trial in the declaration of the trial block. The callback will trigger whenever a trial in that block ends. No parameters will be passed into the callback function.
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#### Sample use
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```javascript
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var block = {
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type: 'single-stim',
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stimuli: ['imgA.png', 'imgB.png'],
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on_finish: function() {
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console.log('The trial just ended.');
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}
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};
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```
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---
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## on_finish (experiment)
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The `on_finish` callback can be declared in the `jsPsych.init` method. The callback will trigger once all trials in the experiment have been run. The method will be passed a single argument, containing all of the data generated in the experiment.
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#### Sample use
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```javascript
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jsPsych.init({
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experiment_structure: exp,
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on_finish: function(data) {
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console.log('The experiment is over! Here is all the data: '+JSON.stringify(data));
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}
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});
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```
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---
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## on_trial_finish
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The `on_trial_finish` callback can be declared in the `jsPsych.init` method. The callback will trigger at the end of every trial in the experiment. If you want a callback to trigger only for the end of certain trials, use the [`on_finish`](#onfinishtrial) callback. There are no parameters passed to the callback function.
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#### Sample use
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```javascript
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jsPsych.init({
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experiment_structure: exp,
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on_trial_finish: function() {
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console.log('A trial just ended.');
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}
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});
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```
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---
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## on_trial_start
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The `on_trial_start` callback can be declared in the `jsPsych.init` method. The callback will trigger at the start of every trial in the experiment. There are no parameters passed to the callback function.
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#### Sample use
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```javascript
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jsPsych.init({
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experiment_structure: exp,
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on_trial_start: function() {
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console.log('A trial just started.');
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}
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});
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```
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