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snippets/deepGetter.md

@@ -0,0 +1,24 @@
+### deepGetter
+
+Returns the target value in a nested JSON object, based on the keys array.
+
+Contrust the keys you want in the nested JSON object as an `Array`.
+Use `Array.prototype.reduce()` to get value from nested JSON object one by one. if the key exists in object, return target value, otherwise, return null.
+
+```js
+const deepGetter = (obj, keys) => keys.reduce((xs, x) => (xs && xs[x]) ? xs[x] : null, obj)
+```
+
+```js
+let idx = 2; // or variable from other places
+const data = {
+  foo: {
+    foz: [1, 2, 3],
+    bar: {
+      baz: ['a', 'b', 'c']
+    }
+  }
+};
+deepGetter(data, ['foo', 'foz', idx]); // get 3
+deepGetter(data, ['foo', 'bar', 'baz', 8, 'foz']); // null
+```

tag_database

@@ -53,6 +53,7 @@ decapitalize:string,array,intermediate
 deepClone:object,recursion,intermediate
 deepFlatten:array,recursion,intermediate
 deepFreeze:object,recursion,intermediate
+deepGetter:object,intermediate
 deepMapKeys:object,recursion,advanced
 defaults:object,intermediate
 defer:function,intermediate

test/deepGetter.test.js

@@ -0,0 +1,40 @@
+const expect = require('expect');
+const {deepGetter} = require('./_30s.js');
+
+let idx = 2
+const data = {
+  level1: {
+    level2: {
+      level3: 'level3',
+      level3a: true,
+      level3b: [1, 2, 3, { level3c: 'level3c' }, 4, 5],
+      level3d: {
+        level4: [{ foo: 'foo' }, { bar: 'bar' }, { baz: 'baz' }]
+      }
+    }
+  }
+};
+
+test('deepGetter is a Function', () => {
+  expect(deepGetter).toBeInstanceOf(Function);
+});
+
+test('deepGetter target success', () => {
+  expect(deepGetter(data, ['level1', 'level2', 'level3'])).toEqual('level3');
+});
+
+test('deepGetter target and return null', () => {
+  expect(deepGetter(data, ['level1', 'level2', 'foo', 'baz'])).toEqual(null);
+});
+
+test('deepGetter target in an array', () => {
+  expect(deepGetter(data, ['level1', 'level2', 'level3d', 'level4', 2, 'baz'])).toEqual('baz');
+});
+
+test('deepGetter target with variable key', () => {
+  expect(deepGetter(data, ['level1', 'level2', 'level3b', idx])).toEqual(3);
+});
+
+test('deepGetter target with empty Object', () => {
+  expect(deepGetter({}, ['foo', 'bar', idx, 'foo'])).toEqual(null);
+});