make count algorithm more efficient

.travis.yml

@@ -2,4 +2,4 @@ branches:
   except: /^v\d/
 language: node_js
 node_js: node
-after_script: node_modules/.bin/nyc report --reporter=text-lcov | npx coveralls
+after_script: node_modules/.bin/nyc report | npx coveralls

index.js

@@ -1,30 +1,64 @@
 'use strict';
 
-var arrIndexesOf = require('arr-indexes-of');
+var appendType = require('append-type');
+
+/*!
+ * repetition-ranges | ISC (c) Shinnosuke Watanabe
+ * https://github.com/shinnn/repetition-ranges
+*/
 
 module.exports = function repetitionRanges(arr, value) {
-	var indexes = arrIndexesOf(arr, value);
+	if (!Array.isArray(arr)) {
+		throw new TypeError('Expected an array, but got ' + appendType(arr) + '.');
+	}
 
 	var results = [];
-	var i = 0;
-	var start = null;
 
-	while (i < indexes.length) {
-		if (indexes[i] === indexes[i + 1] - 1) {
+	if (arr.length < 2) {
+		return results;
+	}
+
+	var i = arr.indexOf(value);
+
+	if (i === -1) {
+		return results;
+	}
+
+	var last = arr.lastIndexOf(value);
+
+	if (i === last) {
+		return results;
+	}
+
+	if (i + 1 === last) {
+		return [{start: i, end: last}];
+	}
+
+	var start = i++;
+
+	do {
+		if (arr[i] !== value) {
+			start = null;
+			continue;
+		}
+
+		if (arr[i + 1] === value) {
 			if (start === null) {
-				start = indexes[i];
+				start = i;
 			}
-		} else if (start !== null) {
+
+			continue;
+		}
+
+		if (start !== null) {
 			results.push({
 				start: start,
-				end: indexes[i]
+				end: i
 			});
-
-			start = null;
 		}
 
-		i += 1;
-	}
+		start = null;
+	} while (i++ < last);
 
 	return results;
 }

index.mjs

@@ -1,28 +1,61 @@
-import arrIndexesOf from 'arr-indexes-of';
+/*!
+ * repetition-ranges | ISC (c) Shinnosuke Watanabe
+ * https://github.com/shinnn/repetition-ranges
+*/
+import appendType from 'append-type';
 
 export default function repetitionRanges(arr, value) {
-	var indexes = arrIndexesOf(arr, value);
+	if (!Array.isArray(arr)) {
+		throw new TypeError('Expected an array, but got ' + appendType(arr) + '.');
+	}
 
 	var results = [];
-	var i = 0;
-	var start = null;
 
-	while (i < indexes.length) {
-		if (indexes[i] === indexes[i + 1] - 1) {
+	if (arr.length < 2) {
+		return results;
+	}
+
+	var i = arr.indexOf(value);
+
+	if (i === -1) {
+		return results;
+	}
+
+	var last = arr.lastIndexOf(value);
+
+	if (i === last) {
+		return results;
+	}
+
+	if (i + 1 === last) {
+		return [{start: i, end: last}];
+	}
+
+	var start = i++;
+
+	do {
+		if (arr[i] !== value) {
+			start = null;
+			continue;
+		}
+
+		if (arr[i + 1] === value) {
 			if (start === null) {
-				start = indexes[i];
+				start = i;
 			}
-		} else if (start !== null) {
+
+			continue;
+		}
+
+		if (start !== null) {
 			results.push({
 				start: start,
-				end: indexes[i]
+				end: i
 			});
-
-			start = null;
 		}
 
-		i += 1;
-	}
+		start = null;
+	} while (i++ < last);
 
 	return results;
 }

package.json

@@ -33,7 +33,7 @@
 		"elements"
 	],
 	"dependencies": {
-		"arr-indexes-of": "^2.0.0"
+		"append-type": "^1.0.1"
 	},
 	"devDependencies": {
 		"@shinnn/eslint-config": "^6.7.1",

test.js

@@ -15,8 +15,8 @@ test('repetitionRanges()', t => {
 	t.deepEqual(arr, ['a', 'b', 'b'], 'should not mutate the passed array.');
 
 	t.deepEqual(
-		repetitionRanges([0, 0, '0', 0, 0, 0, Buffer.from('0'), null, undefined], 0),
-		[{start: 0, end: 1}, {start: 3, end: 5}],
+		repetitionRanges([0, 0, '0', 0, 0, 0, Buffer.from('0'), null, undefined, 0, 0], 0),
+		[{start: 0, end: 1}, {start: 3, end: 5}, {start: 9, end: 10}],
 		'should get multiple positions if exist.'
 	);
 
@@ -32,6 +32,12 @@ test('repetitionRanges()', t => {
 		'should return an empty array if the search value doesn\'t exist in the array.'
 	);
 
+	t.deepEqual(
+		repetitionRanges([1, 2, 3], 1),
+		[],
+		'should return an empty array if the search value appears only once.'
+	);
+
 	t.deepEqual(
 		repetitionRanges([], true),
 		[],