Allow numeric steps when retrieving array elemetn

src/__tests__/get.spec.ts

@@ -0,0 +1,79 @@
+import {get} from '../get';
+import {test, expect} from 'vitest';
+import {parseJsonPointer} from '../util';
+
+test('can find number root', () => {
+  const res = get(123, []);
+  expect(res).toBe(123);
+});
+
+test('can find string root', () => {
+  const res = get('foo', []);
+  expect(res).toBe('foo');
+});
+
+test('can find key in object', () => {
+  const res = get({foo: 'bar'}, ['foo']);
+  expect(res).toBe('bar');
+});
+
+test('can retrieve withing deep object', () => {
+  const res = get({foo: {bar: {baz: 'qux', a: 1}}}, ['foo', 'bar', 'baz']);
+  expect(res).toEqual('qux');
+});
+
+test('simple key in simple object', () => {
+  const doc = {a: 123};
+  const path = parseJsonPointer('/a');
+  const res = get(doc, path);
+  expect(res).toEqual(123);
+});
+
+test('returns "undefined" when referencing missing key with multiple steps', () => {
+  const doc = {a: 123};
+  const path = parseJsonPointer('/b/c');
+  expect(get(doc, path)).toBe(undefined);
+});
+
+test('can reference array element', () => {
+  const doc = {a: {b: [1, 2, 3]}};
+  const path = parseJsonPointer('/a/b/1');
+  const res = get(doc, path);
+  expect(res).toEqual(2);
+});
+
+test('returns "undefined" when referencing end of array', () => {
+  const doc = {a: {b: [1, 2, 3]}};
+  const path = parseJsonPointer('/a/b/-');
+  const res = get(doc, path);
+  expect(res).toBe(undefined);
+});
+
+test('returns undefined when pointing past array boundary', () => {
+  const doc = {a: {b: [1, 2, 3]}};
+  const path = parseJsonPointer('/a/b/-1');
+  expect(get(doc, path)).toBe(undefined);
+});
+
+test('missing object key returns undefined', () => {
+  const doc = {foo: 123};
+  const path = parseJsonPointer('/bar');
+  const res = get(doc, path);
+  expect(res).toBe(undefined);
+});
+
+test('can reference array element by number step', () => {
+  const doc = [1, 2, 3];
+  expect(get(doc, [0])).toBe(1);
+  expect(get(doc, [1])).toBe(2);
+  expect(get(doc, [2])).toBe(3);
+  expect(get(doc, [3])).toBe(undefined);
+});
+
+test('can reference array element by number step', () => {
+  const doc = {foo: {bar: [1, 2, 3]}};
+  expect(get(doc, ['foo', 'bar', 0])).toBe(1);
+  expect(get(doc, ['foo', 'bar', 1])).toBe(2);
+  expect(get(doc, ['foo', 'bar', 2])).toBe(3);
+  expect(get(doc, ['foo', 'bar', 3])).toBe(undefined);
+});

src/get.ts

@@ -8,11 +8,12 @@ export const get = (val: unknown, path: Path): unknown | undefined => {
   for (let i = 0; i < pathLength; i++) {
     key = path[i];
     if (val instanceof Array) {
-      if (key === '-') return undefined;
-      const key2 = ~~key;
-      if ('' + key2 !== key) return undefined;
-      key = key2;
-      if (key < 0) return undefined;
+      if (typeof key !== 'number') {
+        if (key === '-') return undefined;
+        const key2 = ~~key;
+        if ('' + key2 !== key) return undefined;
+        key = key2;
+      }
       val = val[key];
     } else if (typeof val === 'object') {
       if (!val || !has(val as object, key as string)) return undefined;