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84 lines
2.8 KiB
Markdown
84 lines
2.8 KiB
Markdown
# Event-related callback functions
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jsPsych offers the ability to call arbitrary functions in response to certain events occurring, 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 at the end of a data update cycle. This happens after every trial, after the on_finish (trial) and on_trial_finish events execute, allowing you to modify the data in those callbacks, and then use this callback to store the data. 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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timeline: 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. The callback will trigger whenever the trial ends. The callback function will be passed a single argument, containing the data object from the trial.
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#### Sample use
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```javascript
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var trial = {
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type: 'single-stim',
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stimulus: 'imgA.png',
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on_finish: function(data) {
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console.log('The trial just ended.');
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console.log(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 (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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timeline: 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 on the trial object. The callback function will be passed a single argument, containing the data object from the trial.
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#### Sample use
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```javascript
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jsPsych.init({
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timeline: exp,
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on_trial_finish: function(data) {
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console.log('A trial just ended.');
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console.log(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_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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timeline: 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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