refactor(state.ts): extract logic to get threshold session index into a separate function for reusability and clarity

assets/ts/main.ts

@@ -14,9 +14,19 @@ initNav()
 if (ijs.length > 0) {
   if (!isMobile()) {
     import('./desktop/init')
-      .then((d) => d.initDesktop(ijs))
-      .catch((e) => console.log(e))
+      .then((d) => {
+        d.initDesktop(ijs)
+      })
+      .catch((e) => {
+        console.log(e)
+      })
   } else {
-    import('./mobile/init').then((m) => m.initMobile(ijs)).catch((e) => console.log(e))
+    import('./mobile/init')
+      .then((m) => {
+        m.initMobile(ijs)
+      })
+      .catch((e) => {
+        console.log(e)
+      })
   }
 }

assets/ts/state.ts

@@ -21,10 +21,8 @@ const thresholds = [
 const defaultState = {
   index: -1,
   length: 0,
-  threshold:
-    thresholds[parseInt(sessionStorage.getItem('thresholdsIndex') || '2')].threshold,
-  trailLength:
-    thresholds[parseInt(sessionStorage.getItem('thresholdsIndex') || '2')].trailLength
+  threshold: thresholds[getThresholdSessionIndex()].threshold,
+  trailLength: thresholds[getThresholdSessionIndex()].trailLength
 }
 
 export const state = new Watchable<State>(defaultState)
@@ -75,7 +73,7 @@ export function decThreshold(): void {
  */
 
 function updateThreshold(state: State, inc: number): State {
-  let i = thresholds.findIndex((t) => state.threshold === t.threshold) + inc
+  const i = thresholds.findIndex((t) => state.threshold === t.threshold) + inc
   // out of bounds
   if (i < 0 || i >= thresholds.length) return state
   // storage the index so we can restore it even if we go to another page
@@ -83,3 +81,9 @@ function updateThreshold(state: State, inc: number): State {
   const newItems = thresholds[i]
   return { ...state, ...newItems }
 }
+
+function getThresholdSessionIndex(): number {
+  const s = sessionStorage.getItem('thresholdsIndex')
+  if (s === null) return 2
+  return parseInt(s)
+}