Added error for undefined types in jsPsych timeline.

packages/lookit-initjspsych/src/errors.ts

@@ -1,3 +1,14 @@
+/**
+ * Needed to tell user that their nth trial was undefined.
+ * https://stackoverflow.com/a/39466341
+ *
+ * @param n - Number needing suffix
+ * @returns Number with ordinal suffix
+ */
+const nth = (n: number) => {
+  return `${n}${["st", "nd", "rd"][((((n + 90) % 100) - 10) % 10) - 1] || "th"}`;
+};
+
 /** Error when experiment data doesn't contain values on finish. */
 export class SequenceExpDataError extends Error {
   /** Error when experiment data doesn't contain values on finish. */
@@ -6,3 +17,16 @@ export class SequenceExpDataError extends Error {
     this.name = "SequenceExpDataError";
   }
 }
+/** When a trial is accidentally undefined. */
+export class UndefinedTypeError extends Error {
+  /**
+   * Inform user that their nth trial is undefined.
+   *
+   * @param idx - Index of timeline where trial type is undefined
+   */
+  public constructor(idx: number) {
+    super(
+      `${nth(idx + 1)} trial has an undefined type.  Maybe the type name is misspelled.`,
+    );
+  }
+}

packages/lookit-initjspsych/src/index.ts

@@ -1,4 +1,5 @@
 import { initJsPsych as origInitJsPsych } from "jspsych";
+import { UndefinedTypeError } from "./errors";
 import { JsPsychOptions, Timeline } from "./types";
 import { on_data_update, on_finish } from "./utils";
 
@@ -39,7 +40,10 @@ const lookitInitJsPsych = (responseUuid: string) => {
      */
     jsPsych.run = function (timeline) {
       // check timeline here...
-      timeline.map((t: Timeline) => {
+      timeline.map((t: Timeline, idx: number) => {
+        if (!t.type) {
+          throw new UndefinedTypeError(idx);
+        }
         addChsData(t);
       });