For the browser you should use bower (https://bower.io):
bower install little-ytlib --save
In NodeJS yarn (https://yarnpkg.com/lang/en/) or npm (... https://nodejs.org/en/):
Yarn: yarn add little-ytlib
NPM: npm install little-ytlib --save

How can I use it now ?

If you want to use it in your browser, you need to include the bundle.min.js

<script src="bower_components/little-ytlib/bundle.min.js"></script>
<script>
  var yt = new YTLib("MY_API_KEY");
  // Now you can use it
</script>

If you want to use it with NodeJS, simply require it:

const YTLib = require('little-ytlib');
const yt = new YTLib("MY_API_KEY");
// Now you can use it

How do I known which methods I can use ?

I think I doucmented the library very good with JSDoc. You can simply look in the source file on this repository (https://raw.githubusercontent.com/TheNoim/YouTubeLibrary/master/YouTubeLibrary.js)

Documentation

Classes

YouTubeLibrary

Typedefs

YouTubeVideoResource : Object
VideoSnippet : Object
VideoStatistics : Object
YouTubePageInfo : Object
searchListResponse : Object
PlaylistInformation : Object
PlaylistSnippet : Object
PlaylistContentDetails : Object
Video : Object
PlayListWithVideos : Object

YouTubeLibrary

Kind: global class
Author: Nils Bergmann nilsbergmann@noim.io

YouTubeLibrary
- new YouTubeLibrary(APIKey)
- .getVideoInformation(videoId, [Callback]) ⇒ Promise.<(VideoSnippet|Array.<VideoSnippet>)>
- .searchOnYouTube(SearchText, [type], [Order], [maxResults], [pages], [nextPageToken]) ⇒ Promise.<searchListResponse>
- .getPlaylistInformation(playlistId, [Callback]) ⇒ Promise.<PlaylistInformation>
- .getPlaylist(playlistId, [Callback]) ⇒ Promise
- .getPlaylistVideos(playlistId, [Callback]) ⇒ Promise.<Array>
- .getChannelID(forUsername, [Callback]) ⇒ Promise.<String>
- .getChannelPlaylists(channelId, [Callback]) ⇒ Promise.<Array.<PlayListWithVideos>>
- .getChannelPlaylistsByUsername(Username, [Callback]) ⇒ Promise.<Array.<PlayListWithVideos>>
- .getChannel(channelID, [Callback]) ⇒ Promise.<Object>
- .getChannelByUsername(Username, [Callback]) ⇒ Promise.<Object>

new YouTubeLibrary(APIKey)

Nils little youtube library

Param	Description
APIKey	API Key to access the youtube data api

youTubeLibrary.getVideoInformation(videoId, [Callback]) ⇒ `Promise.<(VideoSnippet|Array.<VideoSnippet>)>`

Get the video information's of the videoId

Kind: instance method of YouTubeLibrary

Param	Type
videoId	`string` \| `array`
[Callback]	`function`

youTubeLibrary.searchOnYouTube(SearchText, [type], [Order], [maxResults], [pages], [nextPageToken]) ⇒ `Promise.<searchListResponse>`

Search on youtube with the given parameters

Kind: instance method of YouTubeLibrary

Param	Type	Default	Description
SearchText	`string`
[type]	`string`	`"video,channel,playlist"`
[Order]	`string`	`"relevance"`
[maxResults]	`int`	`20`	Max result per page
[pages]	`int`	`10`	how many pages to query
[nextPageToken]	`string`

youTubeLibrary.getPlaylistInformation(playlistId, [Callback]) ⇒ `Promise.<PlaylistInformation>`

Get all important information's of a playlist

Kind: instance method of YouTubeLibrary

Param	Type
playlistId	`string`
[Callback]	`function`

youTubeLibrary.getPlaylist(playlistId, [Callback]) ⇒ `Promise`

Get all information's of a playlist including the videos. The videos are resolved to youtube#video

Kind: instance method of YouTubeLibrary

Param	Type
playlistId	`string`
[Callback]	`function`

youTubeLibrary.getPlaylistVideos(playlistId, [Callback]) ⇒ `Promise.<Array>`

Get only the resolved videos of a playlist. Videos are in the format youtube#video

Kind: instance method of YouTubeLibrary

Param	Type
playlistId	`string`
[Callback]	`function`

youTubeLibrary.getChannelID(forUsername, [Callback]) ⇒ `Promise.<String>`

Get the channelId of an username

Kind: instance method of YouTubeLibrary

Param	Type
forUsername	`string`
[Callback]	`function`

youTubeLibrary.getChannelPlaylists(channelId, [Callback]) ⇒ `Promise.<Array.<PlayListWithVideos>>`

Get all playlist's of a channel. The videos are in the format youtube#video

Kind: instance method of YouTubeLibrary

Param	Type
channelId	`string`
[Callback]	`function`

youTubeLibrary.getChannelPlaylistsByUsername(Username, [Callback]) ⇒ `Promise.<Array.<PlayListWithVideos>>`

Same as getChannelPlaylists() but you can use the channel username instead of the channel id

Kind: instance method of YouTubeLibrary

Param	Type
Username	`string`
[Callback]	`function`

youTubeLibrary.getChannel(channelID, [Callback]) ⇒ `Promise.<Object>`

Get channel information's

Kind: instance method of YouTubeLibrary

Param	Type
channelID	`string`
[Callback]	`function`

youTubeLibrary.getChannelByUsername(Username, [Callback]) ⇒ `Promise.<Object>`

Same as getChannel() but you can use the channel username instead of the channel id

Kind: instance method of YouTubeLibrary

Param	Type
Username
[Callback]	`function`