Merge pull request #2 from maximumhallinan/support_negative_indices

Add support for negative indices

index.js

@@ -1,14 +1,19 @@
 'use strict';
 var arrify = require('arrify');
 var numSort = require('num-sort');
+var arrayUniq = require('array-uniq');
 
 module.exports = function (str, i, opts) {
 	opts = opts || {};
 
 	var ret = [];
 	var lastIndex = 0;
 
-	arrify(i).sort(numSort.asc).forEach(function (el) {
+	arrayUniq(arrify(i).map(function (el) {
+		var val = el < 0 ? ((str.length - 1) - (el * -1)) : el;
+
+		return val < 0 ? (val * -1) : val;
+	}).sort(numSort.asc)).forEach(function (el) {
 		el++;
 		ret.push(str.slice(lastIndex, opts.remove ? el - 1 : el));
 		lastIndex = el;

package.json

@@ -30,6 +30,7 @@
     "indices"
   ],
   "dependencies": {
+    "array-uniq": "^1.0.2",
     "arrify": "^1.0.0",
     "num-sort": "^1.0.0"
   },

readme.md

@@ -18,6 +18,9 @@ var splitAt = require('split-at');
 splitAt('unicorn', 2);
 //=> ['uni', 'corn']
 
+splitAt('unicorn', -2);
+//=> ['unico', 'rn']
+
 splitAt('unicorn&rainbow', [6, 7]);
 //=> ['unicorn', '&', 'rainbow']
 
@@ -40,7 +43,7 @@ String to be split.
 
 Type: `number`, `array` of `number`
 
-One or more indices.
+One or more indices. A negative index is a 1-based position from the end of the string. For example, -1 is the index of the last place in the string. Duplicate indices are removed from the `index` array. A negative index and positive index that refer to the same position in the string are treated as duplicates.
 
 #### options
 

test.js

@@ -5,16 +5,28 @@ var splitAt = require('./');
 
 test('splitAt()', function (t) {
 	assert.deepEqual(splitAt('unicorn', 2), ['uni', 'corn']);
+	assert.deepEqual(splitAt('unicorn', -2), ['unico', 'rn']);
 
 	assert.deepEqual(
 		splitAt('unicorn & rainbows', [6, 13, 2, 9]),
 		['uni', 'corn', ' & ', 'rain', 'bows']
 	);
 
+	assert.deepEqual(
+		splitAt('unicorn & rainbows', [-6, -13, -2, -9]),
+		['unico', 'rn &', ' ra', 'inbo', 'ws']
+	);
+
 	assert.deepEqual(splitAt('unicorn', 5), ['unicor', 'n']);
 	assert.deepEqual(splitAt('unicorn', 6), ['unicorn']);
+
+	assert.deepEqual(splitAt('unicorn', -1), ['unicor', 'n']);
+
 	assert.deepEqual(splitAt('unicorn', 100), ['unicorn']);
+	assert.deepEqual(splitAt('unicorn', -100), ['unicorn']);
 
+	assert.deepEqual(splitAt('unicorn', [-4, 2]), [ 'uni', 'corn' ]);
+
 	t.end();
 });
 
@@ -24,6 +36,11 @@ test('remove option', function (t) {
 		['unicorn', 'rainbow']
 	);
 
+	assert.deepEqual(
+		splitAt('unicorn&rainbow', -7, {remove: true}),
+		['unicorn', 'rainbow']
+	);
+
 	assert.deepEqual(
 		splitAt('foo|bar|baz', [3, 7], {remove: true}),
 		['foo', 'bar', 'baz']