倒计时

 function gettimer(y,m,d){  
 var now_date = new Date().getTime();  
 var future_date = new Date(y,m,d).getTime();  
 var cha = future_date - now_date;  
var day = Math.floor( cha / 1000 / 60 / 60 / 24);  
 var hours = Math.floor(cha / 1000 / 60 / 60 % 24);  
var minuters = Math.floor(cha / 1000 / 60 % 60);  
 var seconds = Math.floor(cha / 1000 % 60);  
console.log(seconds);  
return `${day < 10 ? '0' + day : day}天${hours}时${minuters}分${seconds < 10 ? '0' + seconds : seconds}秒`;  
}  
var h1 = document.getElementById('time');  
var nt = gettimer(2019,12,30);  
h1.innerHTML = nt;  
setInterval(() => {  
var nt = gettimer(2019,12,30);  
h1.innerHTML = nt;  
}, 1000);  
console.log(gettimer(2019,12,30));  

判断字符串是否对称

var arr = 'aahhba';  
function isSame(list){  
if(list.length % 2 != 0){  
return ;  
}  
for(var i = 0; i < list.length; i++){  
if(list.charAt(i) !== list.charAt(list.length - 1 -i)){  
return 'no';  
}  
}  
return 'ok';  
}  
console.log(isSame(arr));  
冒泡（数组）  
 var arr = [24,22,3,44,9];  
 for(var i = 0; i < arr.length; i++){  
 for(var j = 0; j < arr.length;j++){  
 if(arr[j] > arr[j + 1]){  
 var newarr = arr[j];  
 arr[j] = arr[j + 1];  
 arr[j + 1] = newarr;  
 }  
 }  
 }  
 console.log(arr);