[added] nth() method

src/common.js

@@ -145,6 +145,13 @@ let common = {
       : $(this, assertLength(this, 'last')[this.length - 1], this)
   },
 
+  nth(n, selector) {
+    n = Math.max(0, Math.min(n, this.length))
+    return selector
+      ? this.find(selector).nth(n)
+      : $(this, assertLength(this, 'nth')[n], this)
+  },
+
   only() {
     if (this.length !== 1)
       throw new Error('The query found: ' + this.length + ' items not 1')

test/common.js

@@ -497,6 +497,22 @@ describe('common', ()=> {
               .should.throw('the method `last()` found no matching elements')
         })
 
+        it('.nth()', ()=> {
+          render(<Example />)
+            .nth(1, 'li')
+            .text().should.equal('item 2')
+
+          render(<Example />)
+            .find('li')
+            .nth(1)
+            .text().should.equal('item 2')
+        })
+
+        it('.nth() should throw if there are no elements', ()=> {
+          ;(() => render(<Example />).nth(0, 'article'))
+              .should.throw('the method `nth()` found no matching elements')
+        })
+
         it('.single()', ()=> {
           render(<Example />).single(Stateless).length.should.equal(1)
           render(<Example />).find(Stateless).single().length.should.equal(1)