https://github.com/ferreiratiago/es7
Playground for ECMAScript 2016 (ES7)
https://github.com/ferreiratiago/es7
ecmascript ecmascript2016 es7 es7-array-prototype-includes es7-exponentiation-operator
Last synced: 3 months ago
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Playground for ECMAScript 2016 (ES7)
- Host: GitHub
- URL: https://github.com/ferreiratiago/es7
- Owner: ferreiratiago
- Created: 2017-03-31T16:56:54.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2017-04-06T07:39:13.000Z (about 8 years ago)
- Last Synced: 2023-09-28T13:57:19.728Z (over 1 year ago)
- Topics: ecmascript, ecmascript2016, es7, es7-array-prototype-includes, es7-exponentiation-operator
- Language: JavaScript
- Homepage: https://github.com/tc39/proposals/blob/master/finished-proposals.md
- Size: 4.88 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# ES7 (ECMAScript 2016)
* [Array.prototype.includes](#arrayprototypeincludes)
* [Exponentiation Operator](#exponentiation-operator)
## Array.prototype.includes
Array `.includes()` determines if an array includes an specified element, returning `true` if it includes, `false` otherwise.
### Syntax
```
includes :: (searchElement, ?fromIndex) -> Boolean
```
### Parameters
* `searchElement` - the element to search on the array.
* `fromIndex` - the index from which the search starts.
### Examples
`includes :: (searchElement) -> Boolean`
```js
[].includes() // false
[].includes(undefined) // false
['foo',3,{}].includes({}) // false
['foo','bar'].includes('zed') // false
[-0].includes(+0) // true
[1,2,3].includes(2) // true
['foo','bar'].includes('foo') // true
[undefined].includes(undefined) // true
```
`includes :: (searchElement, fromIndex >= 0) -> Boolean`
```js
['foo','bar','zed'].includes('foo') // true - fromIndex 0 by default
['foo','bar','zed'].includes('foo',1) // false
['foo','bar','zed'].includes('bar',1) // true
// If the fromIndex is greater or equal to the array size,
// the array is not searched and false is returned.
['foo','bar','zed'].includes('bar',10) // false
```
`includes :: (searchElement, fromIndex < 0) -> Boolean`
```js
// When fromIndex is negative a computed index is calculated to be used.
// If the computed index if less than 0, the entire array is search.
// The computation goes like this:
// Computed index = Array length + fromIndex
// e.g.
var array = ['a','b','c','d'] // length = 4
array.includes('b', -3) // computed index = 4 + (-3) = 1, result = true
array.includes('b', -1) // computed index = 4 + (-1) = 3, result = false
array.includes('b', -10) // computed index = 4 + (-10) = -6, result = false
```
### Further Reading
[Array.prototype.includes](https://github.com/tc39/Array.prototype.includes/) (Domenic Denicola, Rick Waldron)
## Exponentiation Operator
Exponentiation operator returns the result of raising the first operand to the power of the second (e.g. `x ** y`).
It will return the same result as `Math.pow(x,y)`.
### Syntax
```
x ** y
```
### Example
```js
// x ** y (aka Math.pow(x,y))
2 ** 2 // 4
2 ** 'a' // NaN
var e = 2
e **= 2 // 4
```
### Further Reading
[Exponentiation Operator](https://github.com/rwaldron/exponentiation-operator) (Rick Waldron)
## Thanks to :beers:
* [2ality.com](http://2ality.com/2016/01/ecmascript-2016.html) by [Axel Rauschmayer](https://twitter.com/rauschma)
* MDN documentation
* [Array.prototype.includes](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/includes)
* [Exponentiation Operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators)