jsPsych ExpBuilder DynamicPlugin

DynamicPlugin is the composable jsPsych plugin used by ExpBuilder to render multiple visual/audio components and response components inside one trial.

Timing system

The current timing implementation uses:

• performance.now() and event timestamps for response timing;
• requestAnimationFrame() with nearest-frame scheduling for visual onset, stimulus duration, trial duration, and frame interval measurement;
• cached preload for current-trial assets;
• ImageBitmap preparation and WebGL textures for timing-critical ImageComponent and plain TextComponent stimuli;
• rAF-only visual commits during active trials;
• explicit DOM interactive-layer auditing for inputs, surveys, uploads, and cloze text;
• background prefetch for upcoming DynamicPlugin trial assets;
• RT from the measured trial onset;
• native capture-phase keydown/pointerdown response timing with event-lag diagnostics;
• per-trial and per-stimulus timing diagnostics, including duration error, dropped-frame estimates, render commit metrics, GPU timer metrics when available, and quality flags.
• diagnostics_level controls whether trials save summary-only data or full debug arrays.

For response trials, read rt/rt_raw as:

response_time - trial_onset_time

rt_corrected is saved separately only when a compatible calibration profile is supplied; rt always remains the raw value.

Read the full timing documentation here:

• TIMING.md

Build

npm run build

The build outputs:

• dist/index.es.js
• dist/index.iife.js