1.写一个方法将数组换成前端更易解析的树状结构
function getTree(data) {
var newData = [],
hash = {};
for (var i = 0; i < data.length; i++) {
if (!hash[data[i].province]) {
hash[data[i].province] = {
\'province\': data[i].province
};
hash[data[i].province][\'city\'] = [{
\'name\': data[i].city,
\'code\': data[i].code
}]
newData.push(hash[data[i].province]);
} else if (hash[data[i].province].province == data[i].province) {
hash[data[i].province][\'city\'].push({
\'name\': data[i].city,
\'code\': data[i].code
})
}
}
return newData;
}var data = [{
\'province\': \'浙江\',
\'city\': \'温州\',
\'code\': \'10010\'
}, { \'province\': \'浙江\',
\'city\': \'杭州\',
\'code\': \'10011\'
}, { \'province\': \'安徽\',
\'city\': \'合肥\',
\'code\': \'10012\'
}, { \'province\': \'安徽\',
\'city\': \'马鞍山\',
\'code\': \'10013\'
}, { \'province\': \'浙江\',
\'city\': \'宁波\',
\'code\': \'10014\'
}];console.log(getTree(data));
2.统计字符串出现最多的字母
function getMax(str) {
var hash = {},
maxstr, max = 1;
for (var i = 0; i < str.length; i++) {
if (!hash[str[i]]) {
hash[str[i]] = 1;
} else {
hash[str[i]]++;
}
if (hash[str[i]] > max) {
max = hash[str[i]];
maxstr = str[i];
}
}
return maxstr;
}
var str = \'abcdeffggghhhhiiiii\';
console.log(getMax(str));
3.排序算法
function bubbleSort(arr) {
for (var i = 0; i < arr.length; i++) {
for (var j = 0; j < arr.length - i - 1; j++) {
if (arr[j] < arr[j + 1]) {
var temp = arr[j + 1];
arr[j + 1] = arr[j];
arr[j] = temp;
}
}
}
return arr;
}
var arr = [1, 2, 8, 3, 4, 1];
console.log(bubbleSort(arr));
4.去重算法
function unique1(arr) {
var newArr = [];
for (var i = 0; i < arr.length; i++) {
if (newArr.indexOf(arr[i]) == -1) {
newArr.push(arr[i]);
}
}
return newArr;
}
var arr1 = [\'b\', \'b\', \'a\', 1, 3, 4, 4];
console.log(unique1(arr1));
function unique2(arr) {
var hash = {},
newArr = [];
for (var i = 0; i < arr.length; i++) {
if (!hash[arr[i]]) {
hash[arr[i]] = true;
newArr.push(arr[i]);
}
}
return newArr;
}
var arr2 = [\'b\', \'b\', \'a\', 1, 3, 4, 4];
console.log(unique2(arr2));
function unique3(arr) {
for (var i = 0; i < arr.length; i++) {
for (var j = 0; j < arr.length; j++) {
if (arr[i] === arr[j] && i != j) {
arr.splice(i, 1);
}
}
}
return arr;
}
var arr3 = [\'b\', \'b\', \'a\', 1, 3, 4, 4];
console.log(unique3(arr3));
5.二分查找算法（建立在已经排好序的情况下）
function binarySearch(arr, data) {
var end = arr.length - 1,
start = 0;
while (start <= end) {
var middle = Math.floor((start + end) / 2);
if (arr[middle] > data) {
end = middle - 1;
} else if (arr[middle] < data) {
start = middle + 1;
} else {
return middle;
}
}
return -1;
}
var arr = [1, 2, 3, 4, 5, 6];
console.log(binarySearch(arr, 2));