increase performance & add benchmark cases

Author: grindcode

README.md

@@ -36,13 +36,13 @@ insert('123', 'yo', 2)
 node benchmark.js
 ```
 ### Results
-```javascript
-insert(string, 'foo', 3)
-// → 11,097,858 ops/sec ±0.70% (84 runs sampled)
-insert(array, 'foo', 3)
-// → 1,015,198 ops/sec ±0.97% (86 runs sampled)
-insert(array, ['foo', undefined, true], 3)
-// → 1,839,994 ops/sec ±0.87% (83 runs sampled)
+```shell
+insert string into string x 10,419,264 ops/sec ±0.77% (84 runs sampled)
+insert 1x array into string x 2,414,477 ops/sec ±0.94% (85 runs sampled)
+insert string into 10x array x 1,672,396 ops/sec ±1.11% (83 runs sampled)
+insert number into 10x array x 1,611,555 ops/sec ±1.49% (80 runs sampled)
+insert object into 10x array x 1,604,038 ops/sec ±2.43% (80 runs sampled)
+insert 3x array into 10x array x 1,636,813 ops/sec ±1.30% (78 runs sampled)
 ```
 
 ## License

benchmark.js

@@ -3,16 +3,25 @@ var Suite = new Benchmark.Suite
 var insert = require('./index.js')
 
 var testString = 'abcdefg'
-var testArray = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
+var testArray = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']
 
 Suite
-  .add('string insert', function () {
+  .add('insert string into string', function () {
     insert(testString, 'foo', 3)
   })
-  .add('array insert string', function () {
+  .add('insert 1x array into string', function () {
+    insert(testString, ['foo', undefined, true], 3)
+  })
+  .add('insert string into 10x array', function () {
     insert(testArray, 'foo', 3)
   })
-  .add('array insert array', function () {
+  .add('insert number into 10x array', function () {
+    insert(testArray, 5, 3)
+  })
+  .add('insert object into 10x array', function () {
+    insert(testArray, { foo: 'bar' }, 3)
+  })
+  .add('insert 3x array into 10x array', function () {
     insert(testArray, ['foo', undefined, true], 3)
   })
   .on('cycle', function (e) {

index.js

@@ -6,9 +6,14 @@
  * @returns {Array|String} New modified value depending on `input` type.
  */
 module.exports = function (input, value, index) {
-  if (typeof input !== 'string' && !Array.isArray(input))
+  var isStringInput = typeof input === 'string'
+  if (!isStringInput && !Array.isArray(input))
     throw new TypeError('First argument invalid. Expected Array or String.')
   if (typeof index !== 'undefined' && typeof index !== 'number')
     throw new TypeError('Third argument invalid. Expected Number.')
-  return input.slice(0, index || 0).concat(value).concat(input.slice(index || 0))
+  // Avoid negative index offset
+  var beacon = index || 0
+  // concat([value]) is faster than concat(value) for String, Number and Object
+  var insert = (Array.isArray(value) || isStringInput)? value: [value]
+  return input.slice(0, beacon).concat(insert).concat(input.slice(beacon))
 }