JS basics-Math array Date

This article explains the basic math array and date related knowledge of js.

1.Math

1. Write a function that returns a random integer from min to max, including min but excluding max

   //不包含最大数
    function getNum(min,max){      //包含最小值，随机最小值与最大值之间的整数且不包含最大值
      console.log(min+Math.floor(Math.random()*(max-min)))
    }
      getNum(10,15)

2. Write a function, Returns a random integer between min and max, including min and max

//Also includes the maximum number

   function getNum2(min,max){    //包含最小值，随机最小值与最大值之间的整数且包含最大值
     console.log(min+Math.floor(Math.random()*(max+1-min)))
}
    getNum2(10,15)

3. Write a function to generate a random number of length n String, the value range of string characters includes 0 to 9, a to z, A to Z.

 function getRandStr(len){    //补全函数
     var str1=''
     var str = &#39;0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ&#39;;     for(var i=0;i<len;i++){       var ss=parseInt(Math.random()*str.length);
           str1 += str[ss];
     }     return str1
  }  var str = getRandStr(10); // 例：0a3iJiRZap
  console.log(str);

4. Write a function to generate a random IP address. A legal IP address is 0.0.0.0~255.255.255.255

 function getRandIP(){    //补全
    var ip=''
    for (var i=0; i<4; i++){      var str=Math.floor(Math.random()*256);
      ip += str;      // 3个点是4个数
      if( i<3 ){
         ip += ".";
      }
   }   return ip;
 }var ip = getRandIP()console.log(ip) // 例：10.234.121.45

5. Write a function to generate a random color character String, the legal color is #000000~ #ffffff

 function getRandColor(){    var str = "0123456789abcdef";    var strlen = str.length;    var colorstr = "#";    for(var i = 0; i < 6; i++){      var index = Math.floor(Math.random()*strlen);
      colorstr += str[strlen];
    }    return colorstr
  }  var color = getRandColor()  console.log(color)   // 例：#3e2f1b

2. Array

1. What are the functions of push, pop, shift, unshift, join, and splice in the array method? Use the splice function to implement the push, pop, shift, and unshift methods respectively.

push(), pop(), unshift(), and shift() are both operations on the array and will change the array itself. length and content.
The difference is that push() and pop() add and delete from the tail of the array, while unshift() and shift() add and delete from the head of the array.

The splice() method adds/removes items to/from the array and returns the removed item. This method mutates the original array.
The join() method is used to put all elements in the array into a string. Elements are separated by the specified delimiter.

//splice函数分别实现push、pop、shift、unshift方法//例子：
  var arr = [1,2,3,4,5]  //push  
  arr.splice(arr.length,0,6); //位置，要删除元素的个数，要添加到数组的元素
  console.log(arr);//[1,2,3,4,5,6]
  console.log(arr.length)  //pop
  arr.splice(arr.length-1,1)  console.log(arr);//[1,2,3,4,5]
  //shift
  arr.splice(0,1);  console.log(arr);//[2,3,4,5]
  //unshift
  arr.splice(0,0,1);  console.log(arr);//[1,2,3,4,5]

2. Write a function to operate the array. Each item in the array becomes the original square and operate on the original array.

 function squareArr(arr){     for(var i = 0; i < arr.length; i++ ){
      arr[i] *= arr[i]
     }     return arr;
   }   var arr = [2, 4, 6]
   squareArr(arr)   console.log(arr) // [4, 16, 36]

3. Write a function to operate the array and return a New array, the new array only contains positive numbers, the original array remains unchanged

  function filterPositive(arr){     var newArr = [];     for(var i = 0; i < arr.length; i++){       if(typeof(arr[i]) === "number" && arr[i] > 0){
         newArr.push(arr[i]);
       }
    }   return newArr;
  }  var arr = [3, -1,  2,  &#39;饥人谷&#39;, true]  var newArr = filterPositive(arr)  console.log(newArr) //[3, 2]

3.Date

1. Write a function getChIntv to get the interval from the current time to the specified date

  function getChIntv(s) {     //时间=指定时间-当前时间
     var time = Math.abs(Date.parse(s) - Date.now()); 
     //天数=时间/天的毫秒
     var days = parseInt(time/(1000*60*60*24));     //几小时=时间%天的毫秒/一小时毫秒
     var hours = parseInt((time%(1000*60*60*24))/(1000*60*60));  
     //几分钟=时间%天的毫秒/一小时毫秒/一分钟毫秒
     var minutes = parseInt(((time%(1000*60*60*24))%(1000*60*60))/(1000*60)); 
    //几秒=时间%天的毫秒/一小时毫秒/一分钟毫秒/一秒毫秒
     var seconds = parseInt(((time%(1000*60*60*24))%(1000*60*60))%(1000*60)/1000); 
     return days + '天' + hours + '小时' + minutes + '分钟' + seconds+ '秒'
   }   var str = getChIntv('2017-7-01'); 
   console.log(str);

2. Change the hh-mm-dd format digital date to Chinese date

 function getChsDate(s) {    
 var arr = ['零','一','二','三','四','五','六','七','八','九','十','十一','十二','十三'    , '十四','十五','十六','十七','十八','十九','二十','二十一','二十二','二十三','二十四',     '二十五','二十六','二十七','二十八','二十九','三十','三十一']    //字符串拆成数组     var time = s.split('-');    // 输出字符串就行    var year = time[0];   
 var month = time[1]; 
   var day = time[2];  
  var newYear = arr[year[0]]+arr[year[1]]+arr[year[2]]; 
   var newMonth = arr[parseInt(month)]; 
   var newDay = arr[parseInt(day)];   
 return newYear+"年"+newMonth+"月"+newDay+"日";  }  var str = getChsDate('2017-06-30');  console.log(str);  // 二零一七年六月三十日

3. Write a function whose parameters are the string format of the milliseconds of the time object, and the return value is a string. Assume that the parameter is the time object milliseconds t, and the following strings are returned according to the time of t:

// Just now (t is less than 1 minute interval from the current time)
// 3 minutes ago (t greater than or equal to 1 minute, less than 1 hour from the current time)
// 8 hours ago (t greater than or equal to 1 hour from the current time, less than 24 hours)
// 3 days ago (t greater than or equal to 24 hours from the current time) hours, less than 30 days)
// 2 months ago (t is greater than or equal to 30 days from the current time and less than 12 months)
// 8 years ago (t is greater than or equal to 12 months from the current time)

// Code:

 function friendlyDate(time){     var msec=new Date()     // getTime()返回距 1970 年 1 月 1 日之间的毫秒数
     var nowTime=msec.getTime()     var sec=(nowTime-time)/1000
     if(sec<60){        return &#39;刚刚&#39;
     }else if(sec>=60&&sec<3600){        return &#39;三分钟前&#39;
     }else if(sec>=3600&&sec<8*3600){        return &#39;8小时前&#39;
     }else if(sec>=24*3600&&sec<24*3600*30){        return &#39;3天前&#39;
     }else if(sec>=24*3600*30&&sec<24*3600*30*12){        return &#39;2个月前&#39;
     }else if(sec>=24*3600*30*12){               return &#39;8年前&#39;     
    }
   }   var str = friendlyDate( &#39;1484286699422&#39; ) 
   var str2 = friendlyDate(&#39;1483941245793&#39;) 
   console.log(str)  //2个月前
   console.log(str2) //2个月前

This article explains the basic knowledge of js. For more knowledge, please pay attention to the php Chinese website.

Related recommendations:

What can jQuery do?

Related knowledge points about front-end cross-domain summary

Common cross-domain solutions for front-end (all)

The above is the detailed content of JS basics-Math array Date. For more information, please follow other related articles on the PHP Chinese website!