Add experimental startSpinner() func

README.md

@@ -383,6 +383,18 @@ echo`Current branch is ${branch}.`
 echo('Current branch is', branch)
 ```
 
+### `startSpinner()`
+
+Starts a simple CLI spinner, and returns `stop()` function.
+
+```js
+import {startSpinner} from 'zx/experimental'
+
+let stop = startSpinner()
+await $`long-running command`
+stop()
+```
+
 ### FAQ
 
 #### Passing env variables

experimental.d.ts

@@ -18,10 +18,12 @@ interface Echo {
   (pieces: TemplateStringsArray, ...args: any[]): void
   (...args: any[]): void
 }
+export const echo: Echo
 
 interface Retry {
   (pieces: TemplateStringsArray, ...args: any[]): Promise<ProcessOutput>
 }
-
-export const echo: Echo
 export const retry: (count: number) => Retry
+
+type StopSpinner = () => void
+export function startSpinner(title: string): StopSpinner

experimental.mjs

@@ -51,3 +51,9 @@ function stringify(arg) {
   }
   return `${arg}`
 }
+
+// Starts a simple CLI spinner, and returns stop() func.
+export function startSpinner(title = '') {
+  let i = 0, spin = () => process.stdout.write(`  ${'⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏'[i++ % 10]} ${title}\r`)
+  return (id => () => clearInterval(id))(setInterval(spin, 100))
+}