摘要：原文鏈接排序算法冒泡排序從小到大排序從大到小排序快速排序這里用，被換過來的必然比小，賦值后直接讓自加，不用再比較，可以提高效率這里用，被換過來的必然比大，賦值后直接讓自減，不用再比較，可以提高效率二路歸并字符串操作判斷回文字

原文鏈接

function bubbleSort(arr){
  var i = 0,
      j = 0;
  for(i=1; i" 從小到大排序
      // "<" 從大到小排序
      if(arr[j] > arr[j+1]){
        temp = arr[j];
        arr[j] = arr[j+1];
        arr[j+1] = temp;
      }
    }
  }
  return arr;
}

function quickSort(arr,l,r){
  if(l < r){
    var i = l, j = r, x = arr[i];
    while(ix)
        j--;
      
      if(i
3、二路歸并
function merge(left, right) {
    var result = [],
        il = 0,
        ir = 0;

    while (il < left.length && ir < right.length) {
        if (left[il] < right[ir]) {
            result.push(left[il++]);
        } else {
            result.push(right[ir++]);
        }
    }
    while(left[il]){
        result.push(left[il++]);
    }
    while(right[ir]){
        result.push(right[ir++]);
    }
    return result;
}
字符串操作
1、判斷回文字符串
function palindrome(str){
  // W匹配任何非單詞字符。等價(jià)于“[^A-Za-z0-9_]”。
  var re = /[W_]/g;
  // 將字符串變成小寫字符,并干掉除字母數(shù)字外的字符
  var lowRegStr = str.toLowerCase().replace(re,"");
  // 如果字符串lowRegStr的length長度為0時(shí)，字符串即是palindrome
  if(lowRegStr.length===0) return true;
  // 如果字符串的第一個(gè)和最后一個(gè)字符不相同，那么字符串就不是palindrome
  if(lowRegStr[0]!=lowRegStr[lowRegStr.length-1]) return false;
  //遞歸
  return palindrome(lowRegStr.slice(1,lowRegStr.length-1));
}
2、翻轉(zhuǎn)字符串
思路一：反向遍歷字符串
function reverseString(str){
  var tmp = "";
  for(var i=str.length-1; i>=0; i--)
    tmp += str[i];
  return tmp
}
思路二：轉(zhuǎn)化成array操作
function reverseString(str){
  var arr = str.split("");
  var i = 0,j = arr.length-1;
  while(i
3、生成指定長度隨機(jī)字符串
function randomString(n){
  var str = "abcdefghijklmnopqrstuvwxyz0123456789";
  var tmp = "";
  for(var i=0; i
4、統(tǒng)計(jì)字符串中次數(shù)最多字母
function findMaxDuplicateChar(str) {
  if(str.length == 1) {
    return str;
  }
  var charObj = {};
  for(var i = 0; i < str.length; i++) {
    if(!charObj[str.charAt(i)]) {
      charObj[str.charAt(i)] = 1;
    } else {
      charObj[str.charAt(i)] += 1;
    }
  }
  var maxChar = "",
      maxValue = 1;
  for(var k in charObj) {
    if(charObj[k] >= maxValue) {
      maxChar = k;
      maxValue = charObj[k];
    }
  }
  return maxChar + "：" + maxValue;
}
數(shù)組操作
1、數(shù)組去重
function unique(arr){
  var obj = {}
  var result = []
  for(var i in arr){
    if(!obj[arr[i]]){
      obj[arr[i]] = true;
      result.push(arr[i]);
    }
  }
  return result;
}
2、數(shù)組中最大差值
function getMaxProfit(arr){
  var min = arr[0],
      max = arr[0];
  for(var i = 0; i < arr.length; i++){
    if(arr[i] < min) min = arr[i];
    if(arr[i] > max) max = arr[i];
  }
  return max - min;
}
其他常見算法
1、階乘
非遞歸實(shí)現(xiàn)
function factorialize(num) {
  var result = 1;
    if(num < 0) return -1;
    if(num == 0 || num == 1) return 1;
    while(num>1) {
      result *= num--;
    }
    return result;
}
遞歸實(shí)現(xiàn)
function factorialize(num) {
  var result = 1;
  if(num < 0) return -1;
  if(num == 0 || num == 1) return 1;
  if(num > 1) return num*factorialize(num-1);
}
2、生成菲波那切數(shù)列
強(qiáng)行遞歸實(shí)現(xiàn)
function getfib(n){
  if(n == 0) return 0;
  if(n == 1) return 1;
  if(n > 1) return getfib(n-1) + getfib(n-2);
}
function fibo(len){
    var fibo = [];
    for(var i = 0; i < len; i++){
      fibo.push(getfib(i));
    }
    return fibo;
}
簡約非遞歸實(shí)現(xiàn)
function getFibonacci(n) {
  var fibarr = [];
  var i = 0;
  while(i < n) {
    if(i <= 1) {
      fibarr.push(i);
    } else {
      fibarr.push(fibarr[i - 1] + fibarr[i - 2])
    }
    i++;
  }
  return fibarr;
}
3、二分查找
非遞歸實(shí)現(xiàn)
function binary_search(arr, key) {
  var low = 0,
      high = arr.length - 1;
  while(low <= high){
    var mid = parseInt((high + low) / 2);
    if(key == arr[mid]){
      return mid;
    }else if(key > arr[mid]){
      low = mid + 1;
    }else if(key < arr[mid]){
      high = mid -1;
    }
  }
  return -1;
}
遞歸實(shí)現(xiàn)
function binary_search2(arr, low, high, key) {
  if(low > high) return -1;
  var mid = parseInt((low + high)/2);
  if(key == arr[mid]) {
    return mid;
  } else if(key > arr[mid]) {
    return binary_search2(arr, mid+1, high, key);
  } else if(key < arr[mid]) {
    return binary_search2(arr, low, mid-1, key);
  }
}