### 1.Fibonacci--

[O(2n)](http://stackoverflow.com/questions/360748/computational-complexity-of-fibonacci-sequence/360773#360773)

```js
function fibonacci(n) {
  return n < 2 ? n : fibonacci(n-1) + fibonacci(n-2); 
}
```

### 2.

```js
function maxInArray(arr) {
  return Math.max.apply(Math, arr);
}
```

### 3. 

```js
String.prototype.reverse = function() {
  return this.split('').reverse().join('');
}
```
or

```js
String.prototype.reverse = function() {
    var str = '';
    var len = this.length;
    while (len>0) {
        str += this.substring(len-1, len);
        len--;
    }
    return str;
}
```

: 'foo  bar'astral symbol,

[ Esrever](https://github.com/mathiasbynens/esrever) 

### 4.DOM



```js
function reverseDom(el){
	var frag = document.createDocumentFragment();
	while(el.lastChild){
		frag.appendChild(el.lastChild);
	}
	el.appendChild(frag);
}
```

DOM

documentFragment

appendChildappendChildDOM,,



### 5.



```js
function removeDuplicateChar(str){
  var strArr = str.split('');
  var targetArr = [];
  strArr.forEach(function(item){
    if (strArr.indexOf(item) === strArr.lastIndexOf(item)) {
      targetArr.push(item)
    }
  })
  
  // 
  return targetArr.join('').split(' ').join('');

}
```

### 6. (palindrome)



Bulid-in Method 
```js
function isPalindrom(str) {
    return str === str.split('').reverse().join('');
}
```


```js
function isPalindrome(str){
  var i, len = str.length;
  // 
  for(i =0; i0){
   count += Math.floor(n/10);
   n = n/10;
  }
  return count;
}
```

### 8.(permutation)

[see](http://www.lifelaf.com/blog/?p=1228)







```js
/**
 * Created by cshao on 12/23/14.
 */

function getPermutation(arr) {
  if (arr.length == 1) {
    return [arr];
  }

  var permutation = [];
  for (var i=0; i