---
title: 101
category: JavaScript libraries
updated: 2017-09-21
intro: |
  [101](https://www.npmjs.com/package/101) is a JavaScript library for dealing with immutable data in a functional manner.
---

### Usage

```js
const isObject = require('101/isObject')
isObject({}) // → true
```

Every function is exposed as a module.

See: [101](https://github.com/tjmehta/101)

### Type checking

```js
isObject({})
isString('str')
isRegExp(/regexp/)
isBoolean(true)
isEmpty({})
isfunction(x => x)
isInteger(10)
isNumber(10.1)
instanceOf(obj, 'string')
```

## Objects
{: .-three-column}

### Example
{: .-prime}

```js
let obj = {}
```

#### Update

```js
obj = put(obj, 'user.name', 'John')
// → { user: { name: 'John' } }
```

#### Read

```js
pluck(name, 'user.name')
// → 'John'
```

#### Delete

```js
obj = del(obj, 'user')
// → { }
```

### Getting

```js
pluck(state, 'user.profile.name')
```

```js
pick(state, ['user', 'ui'])
pick(state, /^_/)
```

`pluck` returns values, `pick` returns subsets of objects.

See:
[pluck](https://github.com/tjmehta/101#pluck),
[pick](https://github.com/tjmehta/101#pick)

### Setting

```js
put(state, 'user.profile.name', 'john')
```

See:
[put](https://github.com/tjmehta/101#put)

### Deleting

```js
del(state, 'user.profile')
omit(state, ['user', 'data'])
```

`omit` is like `del`, but supports multiple keys to be deleted.

See:
[omit](https://github.com/tjmehta/101#omit),
[del](https://github.com/tjmehta/101#del)

### Keypath check

```js
hasKeypaths(state, ['user'])
hasKeypaths(state, { 'user.profile.name': 'john' })
```

See:
[hasKeypaths](https://github.com/tjmehta/101#haskeypaths)

### Get values

```js
values(state)
```

## Functions

### Simple functions

| `and(x, y)` | `x && y` |
| `or(x, y)` | `x || y` |
| `xor(x, y)` | `!(!x && !y) && !(x && y)` |
| `equals(x, y)` | `x === y` |
| `exists(x)` | `!!x` |
| `not(x)` | `!x` |

Useful for function composition.

See:
[and](https://github.com/tjmehta/101#and),
[equals](https://github.com/tjmehta/101#equals),
[exists](https://github.com/tjmehta/101#exists)

### Composition

```js
compose(f, g)       // x => f(g(x))
curry(f)            // x => y => f(x, y)
flip(f)             // f(x, y) --> f(y, x)
```

See:
[compose](https://github.com/tjmehta/101#compose),
[curry](https://github.com/tjmehta/101#curry),
[flip](https://github.com/tjmehta/101#flip)

### And/or

```js
passAll(f, g)       // x => f(x) && g(x)
passAny(f, g)       // x => f(x) || g(x)
```

See:
[passAll](https://github.com/tjmehta/101#passall),
[passAny](https://github.com/tjmehta/101#passany)

### Converge

```js
converge(and, [pluck('a'), pluck('b')])(x)
```

```js
// → and(pluck(x, 'a'), pluck(x, 'b'))
```

See:
[converge](https://github.com/tjmehta/101#converge)

## Arrays

### Finding

```js
find(list, x => x.y === 2)
findIndex(list, x => ...)
includes(list, 'item')
last(list)
```

```js
find(list, hasProps('id'))
```

### Grouping

```js
groupBy(list, 'id')
indexBy(list, 'id')
```

## Examples

### Function composition

```js
isFloat = passAll(isNumber, compose(isInteger, not))
// n => isNumber(n) && not(isInteger(n))
```

```js
function doStuff (object, options) { ... }

doStuffForce = curry(flip(doStuff))({ force: true })
```

## Reference

- <https://github.com/tjmehta/101>