function show_fixation() {
      // show fixation
      //var fixation = paper.image(trial.fixation_image, fix_loc[0], fix_loc[1], trial.fixation_size[0], trial.fixation_size[1]);
      paper.innerHTML += "<img src='"+trial.fixation_image+"' style='position: absolute; top:"+fix_loc[0]+"px; left:"+fix_loc[1]+"px; width:"+trial.fixation_size[0]+"px; height:"+trial.fixation_size[1]+"px;'></img>";

      // wait
      jsPsych.pluginAPI.setTimeout(function() {
        // after wait is over
        show_search_array();
      }, trial.fixation_duration);
    }
jspsych-visual-search-circle
Josh de Leeuw

display a set of objects, with or without a target, equidistant from fixation
subject responds to whether or not the target is present

based on code written for psychtoolbox by Ben Motz

documentation: docs.jspsych.org