关于js的零碎东西（3）
2018-10-07 本文已影响0人
战神七小姐
添加值：.unshift() .push()//返回的不是数值，是追加完成后的数组的长度
.unshift()//在元素前面添加
var a=["abc","as","df"];
a.unshift(["dcfv"]);
console.log(a);//["dcfv","abc","as","df"]
.push()//在元素后面加
var a=["abc","as","df"];
a.push(["dcfv"]);
console.log(a);//["abc","as","df","dcfv"]
删除值：.shift() .pop() //返回值为删除的元素
.shift()//在元素前面开始删
var a=["abc","as","df"];
console.log(a.shift("as"));//as
console.log(a)//["as","df"]
.pop()//在元素后面删
var a=["abc","as","df"];
console.log(a.pop("as"));//as
console.log(a)//["abc","as"]
数组的链接：.concat()
var a=["abc","as","df"];
var b=a.concat(["scd","dcf","rty"]);
console.log(b);//["abc","as","df","scd","dcf","rty"]
翻转值：reverse()
var arr=[1,2,3,4];
console.log(arr.reverse());//4,3,2,1
数组排序：.sort()//返回的是排序后的数组
var a=[1,30,40,5,80];
console.log(a.sort());//1,30,40,5,80
.sort()方法接收一个函数
var a=[12,34,01,32];
console.log(a.sort(function(a,b){
return a>b;//=a-b
}))//01,12,32,34从小往大排//b>a==b-a从大往小排
截数组：.slice() 和字符分.slice()的使用方式一样。区别：数组的返回值是截取出来的新数组，但对原值无影响
var a="frgt";
console.log(a.slice(1));//rgt
console.log(a.slice(2));//gt
splice：
删除数组值：.splice(开始下标，长度)，返回值：删除的数组
添加数组值：.splice(开始下标，0，值1，值2...)返回值：[];
替换数组值：.splice(开始下标，长度，值1，值2...)
对象：arguments
实参自动形成一个类数组，名字为arguments是一组实参的集合
arguments.length 实参的个数
arguments[0] 第一个实参
arguments[arguments.length-1]最后一个实参下标从0开始
10.函数
1.封装indexOf()
var arr=["a","b","c",123,456,"a","b"];
function brr(n,str){
for(var i=0;i<str.length;i++){
if(str[i]==n){
return i;
break;
}
}
return -9;
}
console.log(brr("a",arr));//0
2.封装reverse()
var arr=["a","b","c",123,456,"a","b"];
function reverses(array){
var brr=[];
for(var i=0;i<array.length;i++){
brr.unshift(array[i]);
}
for(var i=array.length-1;i>=0;i--){
brr.push(array[i]);
}
return brr;
}
console.log(reverses(arr));//["b","a",456,123,"c","b","a"]
3.数组排重
<1>.
var arr=[1,2,3,3,4,5,4,6,6,7,8,9,]//[1,2,3,4,5,6,7,8,9]
function abc(str){
var brr=[];
for(var i in str){
if(brr.indexOf(str[i]==-1)){
brr.push(str[i]);
}
}
return brr;
}
console.log(abc(arr));
4.倒计时
var hs=document.getElementById("hs");
var year=document.getElementById("year");
console.log(year.value);
var timer=null;
timer=setInterval(function(){
var oDate=new Date();//当前日期
var eDate=new Date("2018,5,27");//未来日期
var cTime=eDate-oDate;//用未来日期减去现在日期 得到时间差
//计算公式
var day=24*60*60*1000;
hours=60*60*1000;
mines=60*1000;
secs=1000;
var days=Math.floor(cTime/day),
hour=Math.floor(cTime%day/hours),
mine=Math.floor(cTime%hours/mine),
sec=Math.floor(cTime%mine/sec);
hs.innerHTML="距离考试还有"+day+"天"+hour+"时"+mine+"分"+sec+"秒"；
},1000)
5.求平均值
function arr(){
var nums=0;
for(var i=0;i<arguments.length;i++){
nums+=arguments[i];
}
console.log(nums/arguments.length);
}
arr(2,3,5,6);
6.获取验证码
<body>
<h1 id="hh">saxx</h1>
<button type="button" id="btn">点击获取验证码</button>
<button type="button" id="btn1">换背景</button>
</body>
//获取验证码
var btn=document.getElementById("btn");
var hh=document.getElementById("hh");
btn.onclick=function(){
var str=[1,2,3,4,5,6,7,8,9,];
var html="";
for(var i=0;i<4;i++){
var strs;
strs=str[Math.floor(Math.random()*str.length)];
html+=strs
}
hh.innerHTML=html
}//换背景
var btn1=document.getElementById("btn1");
btn1.onclick=function(){
var arr=[1,2,3,4,5,6,7,8,9,0,"a","s","d","f","g","q","w","e","r"];
var arrs="#";
for(var i=0;i<6;i++){
var brr=arr[Math.floor(Math.random()*arr.length)];
arrs+=brr;
}
document.body.style.background=arrs;
}
