Allow calling merge.all with only one element

Fixes #71

index.js

@@ -51,14 +51,13 @@ function deepmerge(target, source, optionsArgument) {
 }
 
 deepmerge.all = function deepmergeAll(array, optionsArgument) {
-	if (!Array.isArray(array) || array.length < 2) {
-		throw new Error('first argument should be an array with at least two elements')
+	if (!Array.isArray(array) || array.length < 1) {
+		throw new Error('first argument should be an array with at least one element')
 	}
 
-	// we are sure there are at least 2 values, so it is safe to have no initial value
 	return array.reduce(function(prev, next) {
 		return deepmerge(prev, next, optionsArgument)
-	})
+	}, {})
 }
 
 module.exports = deepmerge

test/merge-all.js

@@ -6,8 +6,15 @@ test('throw error if first argument is not an array', function(t) {
 	t.end()
 })
 
-test('throw error if first argument is an array with least than two elements', function(t) {
-	t.throws(merge.all.bind(null, [{ example: true }]), Error)
+test('throw error if first argument is an array with no elements', function(t) {
+	t.throws(merge.all.bind(null, []), Error)
+	t.end()
+})
+
+test('Work just fine if first argument is an array with least than two elements', function(t) {
+	var actual = merge.all([{ example: true }])
+	var expected = { example: true }
+	t.deepEqual(actual, expected)
 	t.end()
 })