Add Add Subtitles To Existing Mux Video Asset as a Workflow TIL

workflow/add-subtitles-to-existing-mux-video-asset.md

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+# Add Subtitles To Existing Mux Video Asset
+
+There is a [JavaScript/TypeScript Mux
+SDK](https://github.com/muxinc/mux-node-sdk) for interacting with Mux via their
+[API](https://docs.mux.com/api-reference).
+
+With a Mux client (initialized from `MUX_ACCESS_TOKEN` and `MUX_SECRET_KEY` in
+our environment), we can destructure `Video` which will allow us to call
+`Video.Assets.createTrack`. We pass that function the ID of an existing video
+asset and then an object of data defining the subtitle track. In this case, it
+is an English subtitle track. We need to point Mux to a `url` where the WebVTT
+formatted subtitles are hosted.
+
+```typescript
+// add-srt-to-specific-video.ts
+
+import Mux from '@mux/mux-node'
+
+require('dotenv-flow').config({
+  default_node_env: 'development',
+})
+
+const assetId = "mux-asset-id" // set this value
+const srtUrl = "https://public-webvtt-file" // set this value
+
+// Set up Mux API Client
+const MUX_ACCESS_TOKEN = process.env.MUX_ACCESS_TOKEN as string
+const MUX_SECRET_KEY = process.env.MUX_SECRET_KEY as string
+const muxClient = new Mux(MUX_ACCESS_TOKEN, MUX_SECRET_KEY)
+const {Video} = muxClient
+
+await Video.Assets.createTrack(assetId, {
+  url: srtUrl,
+  type: 'text',
+  text_type: 'subtitles',
+  closed_captions: false,
+  language_code: 'en-US',
+  name: 'English',
+  passthrough: 'English',
+})
+```
+
+We can run the above script with `ts-node` from the command-line like so:
+
+```bash
+$ npx ts-node --files --skipProject add-srt-to-specific-video.ts
+```
+
+We'll see the new track on the existing asset in the Mux dashboard.