I do a great deal of web-based research and have created some open-source code for this that integrates with the popular JavaScript library jsPsych. Below is a list of these projects. If you need help using one of these, or if you want one of them to have some additional functionality, please contact me.
Inclusion of Other in the Self (IOS) Scale
This scale, introduced by Aron et al. (1992), measures interpersonal closeness by having participants select a degree of overlap between two circles that best represents their relationship to another person. I created a jsPsych plugin based on code written by Floris van Vugt to implement a continuous variant of this scale. The source code and documentation are on jspsych-contrib here and you can try a demonstration here. The plugin can also be used to measure closeness to a group, as shown here. In order to avoid biasing participants toward whatever response is shown initially, it is possible to initially hide the circles until the participant's cursor moves over them, as shown here. If you use this tool, please cite the preprint that describes it.
Two-step human reinforcement learning task
The two-step task, originally introduced by Daw et al., is a Markov decision process that elicits different response patterns from model-free and model-based reinforcement learning algorithms. It is used to quantify the contribution of model-free and model-based strategies to human decision making. I wrote a small JavaScript module to easily add this task to a larger jsPsych-based experiment; the source code and documentation is on my GitHub here. You can try a demonstration with very brief instructions here and one with longer, interactive instructions here. If you use this tool, please cite the preprint that describes it.
Visual analogue scale
Visual analogue scales allow research participants to specify responses on a continuous scale. I wrote a jsPsych plugin to collect visual analogue scale ratings; the source code and documentation is on jspsych-contrib here and you can try a demonstration here. I also wrote a preprint describing this tool and its advantages over alternative methods. Please cite this preprint if you use the plugin.
Libet clock for measuring intentional binding
"Intentional binding" refers to an illusory compression of the time between an intentional action and its effect. This phenomenon is thought to be related to sense of agency. One way to measure it involves collecting timing judgments from participants using a Libet clock, and I created a jsPsych plugin to do so. The source code and documentation is on jspsych-contrib here and you can try a demonstration here. We also published a paper demonstrating that the tool is able to measure intentional binding. Please cite this paper if you use the plugin.