#天天小记
最近10天内容
##2017.2.4
###温习数组排序的各种方法
以下以升序为例，使用JS实现：
冒泡排序：通过两两比较，左边若大于右边数字，则左右交换，最小的数字可通过不断交换，“冒泡”到最右边
function bubbleSort(arr){
if(arr.length<=1){return arr;}
for(var i = arr.length;i>0; i--){
for(var j = 0;j<i;j++){
var left = arr[j];
var right = arr[j+1];
if(left > right){
arr[j] = right;
arr[j+1] = left;
}
}
}
return arr;
}
快速排序：取数组中间数字，遍历其他数字，若小于则放在左边数组，大于或等于则放在右边数组，以此递归，将小数组依次拼接成排好序的数组
function quickSort(arr){
if(arr.length<=1){return arr;}
var halfIndex = Math.floor(arr.length / 2);
var halfNum = arr.splice(halfIndex,1)[0];
var left = [];
var right = [];
arr.forEach(function(num){
if(num < halfNum){
left.push(num);
}else{
right.push(num);
}
});
return quickSort(left).concat(halfNum,quickSort(right));
}
插入排序：将没排好的数字依次与排好数组中的数字比较，若小于则插到其前面，否则继续比较直到放到最后
function insertSort(arr){
if(arr.length<=1){return arr;}
var res = [arr[0]];
for(var i=1;i<arr.length;i++){
var cNum = arr[i];
for(var j=0;j<res.length;j++){
var num = res[j];
if(cNum<num){
res.splice(j,0,cNum);
break;
}
if(j==res.length-1){
res.push(cNum);
break;
}
}
}
return res;
}
选择排序：每一次将待排序中最小数取出，放到已排序的最后一个
function selectSort(arr){
if(arr.length<=1){return arr;}
for(var i=0;i<arr.length;i++) {
var min = arr[i];
for (var j=i+1;j<arr.length;j++) {
if(arr[j]<min) {
var temp = min;
min = arr[j];
arr[j] = temp;
}
}
arr[i] = min;
}
return arr;
}
Js自带: Array.sort()
function sortNumber(a,b){
return a-b;
}
console.log([1,10,2,40,3].sort(sortNumber));//[1,2,3,10,40]
###将url参数解析为key:value型的obj
function urlQuery(url){
url = url==null ? window.location.href : url;
var queryArr = url.substring(url.lastIndexOf("?")+1).split("&");
var res = {};
queryArr.forEach(function(item,index){
var param = item.indexOf("=");
var key = decodeURIComponent(item.substring(0,param));
var val = decodeURIComponent(item.substring(param+1));
key ? (res[key] = val) : null;
})
console.log(res);
return res;
}
##2017.2.6
###手写Function.bind函数
bind函数核心：改变函数上下文this,
关注点：保持this，arguments，返回值
MDN的标准polyfill
if (!Function.prototype.bind) {
Function.prototype.bind = function (oThis) {
if (typeof this !== "function") {
// closest thing possible to the ECMAScript 5
// internal IsCallable function
throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable");
}
var aArgs = Array.prototype.slice.call(arguments, 1),
fToBind = this,
fNOP = function () {},
fBound = function () {
return fToBind.apply(this instanceof fNOP
? this
: oThis || this,
aArgs.concat(Array.prototype.slice.call(arguments)));
};
fNOP.prototype = this.prototype;
fBound.prototype = new fNOP();
return fBound;
};
}
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