0
# Lodash KeysIn
1

2
The lodash method `_.keysIn` exported as a module that creates an array of the own and inherited enumerable property names of an object. This utility function is essential for deep object inspection and property enumeration across inheritance chains.
3

4
## Package Information
5

6
- **Package Name**: lodash.keysin
7
- **Package Type**: npm
8
- **Language**: JavaScript
9
- **Installation**: `npm install lodash.keysin`
10

11
## Core Imports
12

13
```javascript
14
const keysIn = require('lodash.keysin');
15
```
16

17
ES6 modules:
18

19
```javascript
20
import keysIn from 'lodash.keysin';
21
```
22

23
## Basic Usage
24

25
```javascript
26
import keysIn from 'lodash.keysin';
27

28
// Simple object
29
keysIn({ 'a': 1, 'b': 2, 'c': 3 });
30
// => ['a', 'b', 'c']
31

32
// Object with inherited properties
33
function Foo() {
34
  this.a = 1;
35
  this.b = 2;
36
}
37

38
Foo.prototype.c = 3;
39

40
keysIn(new Foo);
41
// => ['a', 'b', 'c'] (iteration order is not guaranteed)
42

43
// Arrays
44
keysIn([1, 2, 3]);
45
// => ['0', '1', '2']
46

47
// Non-object values are coerced to objects
48
keysIn('hello');
49
// => ['0', '1', '2', '3', '4']
50
```
51

52
## Capabilities
53

54
### KeysIn Function
55

56
Creates an array of the own and inherited enumerable property names of object.
57

58
```javascript { .api }
59
/**
60
 * Creates an array of the own and inherited enumerable property names of object.
61
 * Non-object values are coerced to objects.
62
 *
63
 * @param {Object} object The object to query.
64
 * @returns {Array} Returns the array of property names.
65
 */
66
function keysIn(object);
67
```
68

69
**Parameters:**
70
- `object` (`Object`): The object to query
71

72
**Returns:**
73
- (`Array`): Returns the array of property names
74

75
**Behavior:**
76
- Coerces non-object values to objects using `Object(object)`
77
- Iterates through all enumerable properties in the object and its prototype chain
78
- Filters out certain internal properties:
79
  - 'constructor' property on prototypes when not explicitly set
80
  - Array-like 'length' property in specific contexts to avoid duplicates with numeric indices
81
- Returns an array containing all qualifying property names
82
- Property iteration order is not guaranteed
83

84
**Usage Examples:**
85

86
```javascript
87
// Object with prototype chain
88
function Animal(name) {
89
  this.name = name;
90
}
91

92
Animal.prototype.species = 'unknown';
93
Animal.prototype.speak = function() {};
94

95
const dog = new Animal('Rex');
96
dog.breed = 'German Shepherd';
97

98
keysIn(dog);
99
// => ['name', 'breed', 'species', 'speak']
100

101
// Array-like objects
102
const arrayLike = { 0: 'a', 1: 'b', length: 2 };
103
keysIn(arrayLike);
104
// => ['0', '1', 'length']
105

106
// Primitive values
107
keysIn(42);
108
// => []
109

110
keysIn('test');
111
// => ['0', '1', '2', '3']
112

113
keysIn(true);
114
// => []
115
```