convert first lib utilities to TypeScript

Convert 6 leaf utility modules from `.js` to `.ts`:
- `noop.ts` — empty function
- `identity.ts` — generic identity function
- `push_unique.ts` — array dedup helper
- `mod.ts` — sanitized modulus functions
- `is_plain_object.ts` — plain object type guard
- `to_log_range.ts` — log scale conversion

esbuild resolves `.ts` files transparently when `.js` is imported,
so no import path changes needed. `tsc --noEmit` passes with zero errors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ryan-williams

src/lib/identity.js

@@ -0,0 +1 @@
+export default function identity<T>(d: T): T { return d; }

src/lib/identity.ts

@@ -0,0 +1,10 @@
+export default function isPlainObject(obj: unknown): obj is Record<string, unknown> {
+    if((globalThis as any).process?.versions) {
+        return Object.prototype.toString.call(obj) === '[object Object]';
+    }
+
+    return (
+        Object.prototype.toString.call(obj) === '[object Object]' &&
+        Object.getPrototypeOf(obj).hasOwnProperty('hasOwnProperty')
+    );
+}

src/lib/is_plain_object.js

@@ -2,7 +2,7 @@
  * sanitized modulus function that always returns in the range [0, d)
  * rather than (-d, 0] if v is negative
  */
-function mod(v, d) {
+export function mod(v: number, d: number): number {
     var out = v % d;
     return out < 0 ? out + d : out;
 }
@@ -11,15 +11,10 @@ function mod(v, d) {
  * sanitized modulus function that always returns in the range [-d/2, d/2]
  * rather than (-d, 0] if v is negative
  */
-function modHalf(v, d) {
+export function modHalf(v: number, d: number): number {
     return Math.abs(v) > (d / 2) ?
         v - Math.round(v / d) * d :
         v;
 }
 
-export { mod, modHalf };
-
-export default {
-    mod: mod,
-    modHalf: modHalf
-};
+export default { mod, modHalf };

src/lib/is_plain_object.ts

@@ -1,8 +1,8 @@
-export default function pushUnique(array, item) {
+export default function pushUnique<T>(array: T[], item: T): T[] {
     if(item instanceof RegExp) {
         var itemStr = item.toString();
         for(var i = 0; i < array.length; i++) {
-            if(array[i] instanceof RegExp && array[i].toString() === itemStr) {
+            if((array[i] as unknown) instanceof RegExp && (array[i] as unknown as RegExp).toString() === itemStr) {
                 return array;
             }
         }

src/lib/mod.js src/lib/mod.tssrc/lib/mod.js renamed to src/lib/mod.ts

@@ -1,11 +1,8 @@
 import isNumeric from 'fast-isnumeric';
 
-export default function toLogRange(val, range) {
+export default function toLogRange(val: number, range: [number, number]): number {
     if(val > 0) return Math.log(val) / Math.LN10;
 
-    // move a negative value reference to a log axis - just put the
-    // result at the lowest range value on the plot (or if the range also went negative,
-    // one millionth of the top of the range)
     var newVal = Math.log(Math.min(range[0], range[1])) / Math.LN10;
     if(!isNumeric(newVal)) newVal = Math.log(Math.max(range[0], range[1])) / Math.LN10 - 6;
     return newVal;