几个前端常见的JS排序代码

function bubbleSort(arr){
 var i = 0,
 j = 0;
 for(i=1; i<arr.length; i++){
 for(j=0; j<=arr.length-i; j++){
 var temp = 0;
 // ">" 从小到大排序
 // "<" 从大到小排序
 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(i<j){
 while(i<j && arr[j]>x)
 j--;
 
 if(i<j)
 //这里用i++，被换过来的必然比x小，赋值后直接让i自加，不用再比较，可以提高效率
 arr[i++] = arr[j];
 
 while(i<j && arr[i]<x)
 i++;
 
 if(i<j)
 //这里用j--，被换过来的必然比x大，赋值后直接让j自减，不用再比较，可以提高效率
 arr[j--] = arr[i];
 }
 arr[i] = x;
 
 quickSort(arr, l, i-1);
 quickSort(arr, i+1, r);
 }
}

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;
}

function palindrome(str){
 // \W匹配任何非单词字符。等价于“[^A-Za-z0-9_]”。
 var re = /[\W_]/g;
 // 将字符串变成小写字符,并干掉除字母数字外的字符
 var lowRegStr = str.toLowerCase().replace(re,'');
 // 如果字符串lowRegStr的length长度为0时，字符串即是palindrome
 if(lowRegStr.length===0) return true;
 // 如果字符串的第一个和最后一个字符不相同，那么字符串就不是palindrome
 if(lowRegStr[0]!=lowRegStr[lowRegStr.length-1]) return false;
 //递归
 return palindrome(lowRegStr.slice(1,lowRegStr.length-1));
}

思路一：反向遍历字符串
function reverseString(str){ 
 var tmp = ''; 
 for(var i=str.length-1; i>=0; i--) 
 tmp += str[i]; 
 return tmp
 }

function reverseString(str){
 var arr = str.split("");
 var i = 0,j = arr.length-1;
 while(i<j){
 tmp = arr[i];
 arr[i] = arr[j];
 arr[j] = tmp;
 i++;
 j--;
 }
 return arr.join("");
}

function randomString(n){
 var str = 'abcdefghijklmnopqrstuvwxyz0123456789';
 var tmp = '';
 for(var i=0; i<n; i++) {
 tmp += str.charAt(Math.round(Math.random()*str.length));
 }
 return tmp;
}

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;
}

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;
}

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;
}

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;
}

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);
}

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;
}

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;
}

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;
}

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);
 }
}