Allow setting prefixText dynamically (#154)

index.d.ts

@@ -18,16 +18,18 @@ declare namespace ora {
 		| 'white'
 		| 'gray';
 
+	type PrefixTextGenerator = () => string;
+
 	interface Options {
 		/**
 		Text to display after the spinner.
 		*/
 		readonly text?: string;
 
 		/**
-		Text to display before the spinner. No prefix text will be displayed if set to an empty string.
+		Text or a function that returns text to display before the spinner. No prefix text will be displayed if set to an empty string.
 		*/
-		readonly prefixText?: string;
+		readonly prefixText?: string | PrefixTextGenerator;
 
 		/**
 		Name of one of the provided spinners. See [`example.js`](https://github.com/BendingBender/ora/blob/master/example.js) in this repo if you want to test out different spinners. On Windows, it will always use the line spinner as the Windows command-line doesn't have proper Unicode support.
@@ -118,11 +120,11 @@ declare namespace ora {
 		readonly text?: string;
 
 		/**
-		Text to be persisted before the symbol. No prefix text will be displayed if set to an empty string.
+		Text or a function that returns text to be persisted before the symbol. No prefix text will be displayed if set to an empty string.
 
 		Default: Current `prefixText`.
 		*/
-		readonly prefixText?: string;
+		readonly prefixText?: string | PrefixTextGenerator;
 	}
 
 	interface Ora {
@@ -137,9 +139,9 @@ declare namespace ora {
 		text: string;
 
 		/**
-		Change the text before the spinner. No prefix text will be displayed if set to an empty string.
+		Change the text or function that returns text before the spinner. No prefix text will be displayed if set to an empty string.
 		*/
-		prefixText: string;
+		prefixText: string | PrefixTextGenerator;
 
 		/**
 		Change the spinner color.

index.js

@@ -189,9 +189,21 @@ class Ora {
 		return this.id !== undefined;
 	}
 
+	getFullPrefixText(prefixText = this[PREFIX_TEXT], postfix = ' ') {
+		if (typeof prefixText === 'string') {
+			return prefixText + postfix;
+		}
+
+		if (typeof prefixText === 'function') {
+			return prefixText() + postfix;
+		}
+
+		return '';
+	}
+
 	updateLineCount() {
 		const columns = this.stream.columns || 80;
-		const fullPrefixText = (typeof this[PREFIX_TEXT] === 'string') ? this[PREFIX_TEXT] + '-' : '';
+		const fullPrefixText = this.getFullPrefixText(this.prefixText, '-');
 		this.lineCount = stripAnsi(fullPrefixText + '--' + this[TEXT]).split('\n').reduce((count, line) => {
 			return count + Math.max(1, Math.ceil(wcwidth(line) / columns));
 		}, 0);
@@ -320,12 +332,11 @@ class Ora {
 
 	stopAndPersist(options = {}) {
 		const prefixText = options.prefixText || this.prefixText;
-		const fullPrefixText = (typeof prefixText === 'string' && prefixText !== '') ? prefixText + ' ' : '';
 		const text = options.text || this.text;
 		const fullText = (typeof text === 'string') ? ' ' + text : '';
 
 		this.stop();
-		this.stream.write(`${fullPrefixText}${options.symbol || ' '}${fullText}\n`);
+		this.stream.write(`${this.getFullPrefixText(prefixText, ' ')}${options.symbol || ' '}${fullText}\n`);
 
 		return this;
 	}

index.test-d.ts

@@ -6,6 +6,7 @@ import {promise} from '.';
 const spinner = ora('Loading unicorns');
 ora({text: 'Loading unicorns'});
 ora({prefixText: 'Loading unicorns'});
+ora({prefixText: () => 'Loading unicorns dynamically'});
 ora({spinner: 'squish'});
 ora({spinner: {frames: ['-', '+', '-']}});
 ora({spinner: {interval: 80, frames: ['-', '+', '-']}});

readme.md

@@ -46,9 +46,9 @@ Text to display after the spinner.
 
 ##### prefixText
 
-Type: `string`
+Type: `string | () => string`
 
-Text to display before the spinner. No prefix text will be displayed if set to an empty string.
+Text or a function that returns text to display before the spinner. No prefix text will be displayed if set to an empty string.
 
 ##### spinner
 

test.js

@@ -357,3 +357,7 @@ test('.stopAndPersist() with manual prefixText', macro, spinner => {
 test('.stopAndPersist() with manual empty prefixText', macro, spinner => {
 	spinner.stopAndPersist({symbol: '@', prefixText: '', text: 'foo'});
 }, /@ foo\n$/, {prefixText: 'bar'});
+
+test('.stopAndPersist() with dynamic prefixText', macro, spinner => {
+	spinner.stopAndPersist({symbol: '&', prefixText: () => 'babeee', text: 'yorkie'});
+}, /babeee & yorkie\n$/, {prefixText: () => 'babeee'});