22 KiB
The jsPsych core library
jsPsych.addNodeToEndOfTimeline
jsPsych.addNodeToEndOfTimeline(node_parameters, callback)
Parameters
| Parameter | Type | Description |
|---|---|---|
| node_parameters | object | An object defining a timeline. It must have, at a minimum, a timeline parameter with a valid timeline array as the value for that parameter. |
| callback | function | An optional callback function. If adding the node to the timeline requires any preloading of media assets, this callback will be triggered after preloading is compelte. |
Return value
None.
Description
Adds the timeline to the end of the experiment.
Examples
Without callback
var trial = {
type: 'html-keyboard-response',
stimulus: 'This is a new trial.'
}
var new_timeline = {
timeline: [trial]
}
jsPsych.addNodeToEndOfTimeline(new_timeline)
With callback
var first = {
type: 'html-keyboard-response',
stimulus: 'first trial; new trial added when on_finish is called',
on_finish: function(){
jsPsych.pauseExperiment();
jsPsych.addNodeToEndOfTimeline({
timeline: [{
type: 'image-keyboard-response',
stimulus: 'img/happy_face_4.jpg'
}]
}, jsPsych.resumeExperiment)
}
}
jsPsych.allTimelineVariables
jsPsych.allTimelineVariables()
Parameters
None.
Return value
Returns an object with all available timeline variables at this moment in the experiment, represented as key: value pairs.
Description
This function can be used to get all the timeline variables at a particular moment in the experiment. Can be useful for annotating data, such as in the example below.
Example
var trial = {
type: 'html-keyboard-response',
stimulus: 'Just a demo',
on_finish: function(data){
// merge all timeline variables available at this trial into the data for this trial
Object.assign(data, jsPsych.allTimelineVariables())
}
}
jsPsych.currentTimelineNodeID
jsPsych.currentTimelineNodeID()
Parameters
None.
Return value
Returns the ID of the TimelineNode that is currently active.
Description
Gets the ID of the active TimelineNode. The ID is a string that follows a specific format:
"0.0"is the ID of the first top-level TimelineNode"1.0"is the ID of the second top-level TimelineNode"2.0"is the ID of the third top-level TimelineNode, and so on...
If a TimelineNode iterates multiple times (using the loop function, for example), then the iterations are indicated in the second number:
"0.0"is the ID of the first top-level TimelineNode during the first iteration"0.1"is the ID of the first top-level TimelineNode during the second iteration"0.2"is the ID of the first top-level TimelineNode during the third iteration, and so on...
If TimelineNodes are nested in other TimelineNodes, then the hierarchical structure is shown with ".":
"0.0-1.0"is the ID of the second TimelineNode on the timeline of the first top-level TimelineNode."0.0-2.0"is the ID of the third TimelineNode on the timeline of the first top-level TimelineNode, and so on...
The rules about iterations apply throughout the hierarchical ID:
"0.2-1.3"is the ID of the second TimelineNode, executing for the fourth time, on the timeline of the first top-level TimelineNode, executing for the third time.
Example
var id = jsPsych.currentTimelineNodeID();
console.log('The current TimelineNode ID is '+id);
jsPsych.currentTrial
jsPsych.currentTrial()
Parameters
None.
Return value
Returns the object describing the current trial. The object will contain all of the parameters associated with the current trial.
Description
Get a description of the current trial
Example
var trial = jsPsych.currentTrial();
console.log('The current trial is using the '+trial.type+' plugin');
jsPsych.endCurrentTimeline
jsPsych.endCurrentTimeline
Parameters
None.
Return value
None.
Description
Ends the current timeline. If timelines are nested, then only the timeline that contains the current trial is ended.
Example
End timeline if a particular key is pressed
var images = [
"img/1.gif", "img/2.gif", "img/3.gif", "img/4.gif",
"img/5.gif", "img/6.gif", "img/7.gif", "img/8.gif",
"img/9.gif", "img/10.gif"
];
var trials = [];
for (var i = 0; i < images.length; i++) {
trials.push({
stimulus: images[i]
});
}
var block = {
type: 'image-keyboard-response',
choices: ['y', 'n'],
prompt: '<p>Press "y" to Continue. Press "n" to end this node of the experiment.</p>',
on_finish: function(data) {
if (data.key_press == 'n') {
jsPsych.endCurrentTimeline();
}
},
timeline: trials
}
var after_block = {
type: 'html-keyboard-response',
stimulus: '<p>The next node</p>'
}
jsPsych.init({
timeline: [block, after_block],
on_finish: function() {
jsPsych.data.displayData();
}
});
jsPsych.endExperiment
jsPsych.endExperiment(end_message)
Parameters
| Parameter | Type | Description |
|---|---|---|
| end_message | string | A message to display on the screen after the experiment is over. |
Return value
None.
Description
Ends the experiment, skipping all remaining trials.
Example
End the experiment if a particular response is given
var trial = {
type: 'image-keyboard-response',
stimulus: 'image1.jpg',
choices: ['y', 'n']
prompt: '<p>Press "y" to Continue. Press "n" to end the experiment</p>',
on_finish: function(data){
if(data.key_press == "n"){
jsPsych.endExperiment('The experiment was ended by pressing "n".');
}
}
}
jsPsych.finishTrial
jsPsych.finishTrial(data)
Parameters
| Parameter | Type | Description |
|---|---|---|
| data | object | The data to store for the trial. |
Return value
Returns nothing.
Description
This method tells jsPsych that the current trial is over. It is used in all of the plugins to end the current trial. When the trial ends a few things happen:
- The data is stored using
jsPsych.data.write() - The on_finish callback function is executed for the trial
- The on_trial_finish callback function is executed
- The progress bar is updated if it is being displayed
- The experiment ends if the trial is the last one (and the on_finish callback function is executed).
- The next trial, if one exists, is started.
Example
// this code would be in a plugin
jsPsych.finishTrial({correct_response: true});
jsPsych.getDisplayElement
jsPsych.getDisplayElement()
Parameters
None.
Return value
Returns the HTML DOM element used for displaying the experiment.
Description
Get the DOM element that displays the experiment.
Example
var el = jsPsych.getDisplayElement();
// hide the jsPsych display
el.style.visibility = 'hidden';
jsPsych.getProgressBarCompleted
jsPsych.getProgressBarCompleted()
Parameters
None.
Return value
Returns a value between 0 and 1 representing how full the progress bar currently is.
Description
Used to get the current value of the progress bar. Works for automated and manual control.
Example
var progress_bar_amount = jsPsych.getProgressBarCompleted();
jsPsych.init
jsPsych.init(settings)
Parameters
| Parameter | Type | Description |
|---|---|---|
| settings | object | The settings object for initializing jsPsych. See table below. |
The settings object can contain several parameters. The only required parameter is timeline.
| Parameter | Type | Description |
|---|---|---|
| timeline | array | An array containing the objects that describe the experiment timeline. See Creating an Experiment: The Timeline. |
| display_element | string | The ID of an HTML element to display the experiment in. If left blank, jsPsych will use the <body> element to display content. All keyboard event listeners are bound to this element. In order for a keyboard event to be detected, this element must have focus (be the last thing that the subject clicked on). |
| on_finish | function | Function to execute when the experiment ends. |
| on_trial_start | function | Function to execute when a new trial begins. |
| on_trial_finish | function | Function to execute when a trial ends. |
| on_data_update | function | Function to execute every time data is stored using the jsPsych.data.write method. All plugins use this method to save data (via a call to jsPsych.finishTrial, so this function runs every time a plugin stores new data. |
| on_interaction_data_update | function | Function to execute every time a new interaction event occurs. Interaction events include clicking on a different window (blur), returning to the experiment window (focus), entering full screen mode (fullscreenenter), and exiting full screen mode (fullscreenexit). |
| on_close | function | Function to execute when the user leaves the page. Can be used, for example, to save data before the page is closed. |
| exclusions | object | Specifies restrictions on the browser the subject can use to complete the experiment. See list of options below. |
| show_progress_bar | boolean | If true, then a progress bar is shown at the top of the page. |
| message_progress_bar | string | Message to display next to the progress bar. The default is 'Completion Progress'. |
| auto_update_progress_bar | boolean | If true, then the progress bar at the top of the page will automatically update as every top-level timeline or trial is completed. |
| show_preload_progress_bar | boolean | If true, then a progress bar is displayed while media files are automatically preloaded. |
| preload_audio | array | An array of audio files to preload before starting the experiment. |
| preload_images | array | An array of image files to preload before starting the experiment. |
| preload_video | array | An array of video files to preload before starting the experiment. |
| max_load_time | numeric | The maximum number of milliseconds to wait for content to preload. If the wait time is exceeded an error message is displayed and the experiment stops. The default value is 60 seconds. |
| max_preload_attempts | numeric | The maximum number of attempts to preload each file in case of an error. The default value is 10. There is a small delay of 200ms between each attempt. |
| use_webaudio | boolean | If false, then jsPsych will not attempt to use the WebAudio API for audio playback. Instead, HTML5 Audio objects will be used. The WebAudio API offers more precise control over the timing of audio events, and should be used when possible. The default value is true. |
| default_iti | numeric | The default inter-trial interval in ms. The default value if none is specified is 0ms. |
| experiment_width | numeric | The desired width of the jsPsych container in pixels. If left undefined, the width will be 100% of the display element. Usually this is the <body> element, and the width will be 100% of the screen size. |
| minimum_valid_rt | numeric | The minimum valid response time for key presses during the experiment. Any key press response time that is less than this value will be treated as invalid and ignored. Note that this parameter only applies to keyboard responses, and not to other response types such as buttons and sliders. The default value is 0. |
| override_safe_mode | boolean | Running a jsPsych experiment directly in a web browser (e.g., by double clicking on a local HTML file) will load the page using the file:// protocol. Some features of jsPsych don't work with this protocol. By default, when jsPsych detects that it's running on a page loaded via the file:// protocol, it runs in safe mode, which automatically disables features that don't work in this context. Specifically, the use of Web Audio is disabled (audio will be played using HTML5 audio instead, even if use_webaudio is true) and video preloading is disabled (both automatic preloading and manual preloading via preload_video). The override_safe_mode parameter defaults to false, but you can set it to true to force these features to operate under the file:// protocol. In order for this to work, you will need to disable web security (CORS) features in your browser - this is safe to do if you know what you are doing. Note that this parameter has no effect when you are running the experiment on a web server, because the page will be loaded via the http:// or https:// protocol. |
| case_sensitive_responses | boolean | If true, then jsPsych will make a distinction between uppercase and lowercase keys when evaluating keyboard responses, e.g. "A" (uppercase) will not be recognized as a valid response if the trial only accepts "a" (lowercase). If false, then jsPsych will not make a distinction between uppercase and lowercase keyboard responses, e.g. both "a" and "A" responses will be valid when the trial's key choice parameter is "a". Setting this parameter to false is useful if you want key responses to be treated the same way when CapsLock is turned on or the Shift key is held down. The default value is false. |
Possible values for the exclusions parameter above.
| Parameter | Type | Description |
|---|---|---|
| min_width | numeric | The minimum width of the browser window. If the width is below this value, a message will be displayed to the subject asking them to maximize their browser window. The experiment will sit on this page until the browser window is large enough. |
| min_height | numeric | Same as above, but with height. |
| audio | boolean | Set to true to require support for the WebAudio API (used by plugins that play audio files). |
Return value
Returns nothing.
Description
This method configures and starts the experiment.
Example
See any of the plugin examples in the examples folder in the GitHub repository.
jsPsych.initSettings
jsPsych.initSettings()
Parameters
None
Return value
Returns the settings object used to initialize the experiment.
Description
Gets the object containing the settings for the current experiment.
Example
var settings = jsPsych.initSettings();
// check the experiment structure
console.log(JSON.stringify(settings.timeline));
jsPsych.pauseExperiment
jsPsych.pauseExperiment()
Parameters
None.
Return value
None.
Description
Pauses the experiment. The experiment will finish the current trial, but will not execute any additional trials until jsPsych.resumeExperiment() is called.
Example
var trial = {
type: 'html-keyboard-response',
stimulus: 'Press p to take a 30 second break. Otherwise, press c to continue immediately.',
choices: ['p','c'],
on_finish: function(data){
if(data.key_press == "p") {
jsPsych.pauseExperiment();
setTimeout(jsPsych.resumeExperiment, 30000);
}
}
}
jsPsych.progress
jsPsych.progress()
Parameters
None.
Return value
Returns an object with the following properties:
| Property | Type | Description |
|---|---|---|
| total_trials | numeric | Indicates the number of trials in the experiment. Note that this does not count possible loops or skipped trials due to conditional statements. |
| current_trial_global | numeric | Returns the trial index of the current trial in a global scope. Every trial will increase this count by 1. |
| percent_complete | numeric | Estimates the percent of the experiment that is complete. Works as expected for experiments without conditional or looping timelines. For complex timelines, the percent is an approximation. |
Description
This method returns information about the length of the experiment and the subject's current location in the experiment timeline.
Example
var progress = jsPsych.progress();
alert('You have completed approximately '+progress.percent_complete+'% of the experiment');
jsPsych.resumeExperiment
jsPsych.resumeExperiment()
Parameters
None.
Return value
None.
Description
Resumes the experiment after a call to jsPsych.pauseExperiment(). If the post trial delay (post_trial_gap) has not yet been reached, then the experiment will not continue until the delay is finished. For example, if post_trial_gap was 10,000ms and jsPsych.resumeExperiment() was called 6,000ms after the previous trial finished, then the experiment would not continue for another 4,000ms.
Example
var trial = {
type: 'html-keyboard-response',
stimulus: 'Press p to take a 30 second break. Otherwise, press c to continue immediately.',
choices: ['p','c'],
on_finish: function(data){
if(data.key_press == "p") {
jsPsych.pauseExperiment();
setTimeout(jsPsych.resumeExperiment, 30000);
}
}
}
jsPsych.setProgressBar
jsPsych.setProgressBar(value)
Parameters
| Parameter | Type | Description |
|---|---|---|
| value | numeric | Proprotion (between 0 and 1) to fill the progress bar. |
Return value
None.
Description
Set the progress bar to a custom amount. Proportion must be between 0 and 1. Values larger than 1 are treated as 1.
Example
jsPsych.setProgressBar(0.85);
jsPsych.startTime
jsPsych.startTime()
Parameters
None.
Return value
Returns a Date object indicating when the experiment began.
Description
Get the time that the experiment began.
Example
var start_time = jsPsych.startTime();
jsPsych.timelineVariable
jsPsych.timelineVariable(variable, call_immediate)
Parameters
| Parameter | Type | Description |
|---|---|---|
| variable | string | Name of the timeline variable |
| call_immediate | bool | This parameter is optional and can usually be omitted. It determines the return value of jsPsych.timelineVariable. If true, the function returns the value of the current timeline variable. If false, the function returns a function that returns the value of the current timeline variable. When call_immediate is omitted, the appropriate option is determined automatically based on the context in which this function is called. When jsPsych.timelineVariable is used as a parameter value, call_immediate will be false. This allows it to be used as a dynamic trial parameter. When jsPsych.timelineVariable is used inside of a function, call_immediate will be true. It is possible to explicitly set this option to true to force the function to immediately return the current value of the timeline variable. |
Return value
Either a function that returns the value of the timeline variable, or the value of the timeline variable, depending on the context in which it is used. See call_immediate description above.
Description
Timeline variables are a powerful technique for generating experiments with repetitive procedures but different parameter values. This function fetches the current value of a particular timeline variable. It must be used in conjunction with a timeline that has timeline variables. See the timeline variable section for details.
Examples
Standard use as a parameter for a trial
var trial = {
type: 'image-keyboard-response',
stimulus: jsPsych.timelineVariable('image')
}
var procedure = {
timeline: [trial],
timeline_variables: [
{image: 'face1.png'},
{image: 'face2.png'},
{image: 'face3.png'},
{image: 'face4.png'}
]
}
Invoking immediately in a function
var trial = {
type: 'html-keyboard-response',
stimulus: function(){
return "<img style='width:100px; height:100px;' src='"+jsPsych.timelineVariable('image')+"'></img>";
}
}
var procedure = {
timeline: [trial],
timeline_variables: [
{image: 'face1.png'},
{image: 'face2.png'},
{image: 'face3.png'},
{image: 'face4.png'}
]
}
Prior to jsPsych v6.3.0, the call_immediate parameter must be set to true when jsPsych.timelineVariable is called from within a function, such as a dynamic parameter:
var trial = {
type: 'html-keyboard-response',
stimulus: function(){
return "<img style='width:100px; height:100px;' src='"+jsPsych.timelineVariable('image', true)+"'></img>";
}
}
var procedure = {
timeline: [trial],
timeline_variables: [
{image: 'face1.png'},
{image: 'face2.png'},
{image: 'face3.png'},
{image: 'face4.png'}
]
}
jsPsych.totalTime
jsPsych.totalTime()
Parameters
None.
Return value
Returns a numeric value indicating the number of milliseconds since jsPsych.init was called.
Description
Gets the total time the subject has been in the experiment.
Example
var time = jsPsych.totalTime();
console.log(time);
jsPsych.version
jsPsych.version
Parameters
None.
Return value
Returns the version number as a string.
Description
Gets the version of jsPsych.
Example
var version = jsPsych.version();
console.log(version);