Created the Mutable token

docs/example/mutable-token.ts

@@ -0,0 +1,22 @@
+import {Events, initSimpleBar, ProgressBar, Tokens} from '@nathanpb/progress'
+
+const messages = ['Stage Bondia', 'Help', 'Foo', 'Bar', 'Cool']
+const bar = new ProgressBar({ total: 100 })
+const token = Tokens.mutable('Initial')
+
+initSimpleBar({
+  bar,
+  template: '[$bar$] $message$',
+  stream: process.stdout,
+  tokens: {
+    bar: Tokens.bar({ length: 30 }),
+    message: token
+  },
+})
+
+bar.on(Events.COMPLETED, () => console.log('Bar completed'))
+
+setInterval(() => bar.tick(1), 500)
+setInterval(() => {
+  token.setValue(messages[Math.floor(Math.random()*messages.length)])
+}, 1500)

docs/examples.md

@@ -12,6 +12,9 @@
 [example/download-lib.ts](/example/download-lib.ts ':include')
 
 
+# Using the Mutable token
+[example/mutable-token.ts](/example/mutable-token.ts ':include')
+
 # Writing a custom token
 [example/qcustom-token.ts](/example/custom-token.ts ':include')
 

docs/tokens.md

@@ -19,6 +19,7 @@ Tokens.progress()
 - [Tokens.title](/api/modules/Tokens.html#title)
 - [Tokens.rate](/api/modules/Tokens.html#rate)
 - [Tokens.eta](/api/modules/Tokens.html#eta)
+- [Tokens.mutable](/api/modules/Tokens.html#mutable)
 
 ## Writing a custom token
 

src/token.ts

@@ -59,3 +59,28 @@ export const eta = (
   { interval = 1, ...other }: { interval?: number } & NumberFormat = {}
 ): Token => bar =>
   formatNumber(bar.eta() / interval, other)
+
+/**
+ * The Mutable token stores an internal string, which can be mutated using the `getValue` and `setValue` methods
+ *
+ * Example:
+ * ```
+ * const token = Tokens.mutable('Foo')
+ * const bar = new ProgressBar()
+ *
+ * console.log(token.getValue()) // Foo
+ * console.log(token(bar)) // Foo
+ *
+ * token.setValue('Bar')
+ * console.log(token.getValue()) // Bar
+ * console.log(token(bar)) // Bar
+ * ```
+ *
+ * @param initialValue The starting value for the token
+ */
+export const mutable = (initialValue: string): (Token & { getValue: ()=>string, setValue: (value: string)=>void }) => {
+  const func = () => initialValue
+  func.setValue = (value: string) => { initialValue = value }
+  func.getValue = () => initialValue
+  return func
+}

test/token.test.ts

@@ -114,4 +114,29 @@ describe('Tokens.ts', () => {
     const bar = new ProgressBar({ title: 'FooBar' })
     it('Should be FooBar', () => expect(bar.title).toEqual('FooBar'))
   })
+
+  describe('#mutable', () => {
+    it('Should render the initial value of Foo', () => {
+      const token = Tokens.mutable('Foo')
+      const bar = new ProgressBar()
+      expect(token(bar)).toEqual('Foo')
+    })
+
+    describe('#setValue plus #getValue', () => {
+      it('Should return the initial value of Foo, then mutate the value to Bar and retrieve it', () => {
+        const token = Tokens.mutable('Foo')
+        expect(token.getValue()).toEqual('Foo')
+        token.setValue('Bar')
+        expect(token.getValue()).toEqual('Bar')
+      })
+    })
+
+    describe('#setValue plus invoker', () => {
+      it('Should mutate the Token\'s value from Foo to Bar', () => {
+        const token = Tokens.mutable('Foo')
+        token.setValue('Bar')
+        expect(token(new ProgressBar())).toEqual('Bar')
+      })
+    })
+  });
 })