Javascript: returns a random number of four digits or letters. It is a javascript random number.

Javascript: returns a random number of four digits or letters. It is a javascript random number.

This section describes how to implement a simple four-digit random number function through code examples.
A simple method is to randomly extract four non-repeating characters from numbers and letters.

The code example is as follows:

function only(ele,arr){  if(arr.length==0){   return true;  }  for(var j=0;j<arr.length;j++){   if(ele==arr[j]){    return false;   }else{    return true;   }  } }  var arr=[0,1,2,3,4,5,6,"a","b","c","d","e","f","g"];  (function(){  var randNum=null;  var old=[];  var str="";  function done(){   randNum=Math.floor(Math.random()*14);   if(only(randNum,old)){    str=str+arr[randNum];    old.push(randNum);   }   else{    done();   }  }  for(var index=0;index<4;index++){   done();  }  console.log(str); })(arr)

The above Code meets our requirements. The following describes the implementation process of the above Code.

I. Code comments:
1. function only (ele, arr) {}, this function can be used to determine whether the specified index has been used, and random numbers are placed repeatedly.
2. if (arr. length = 0) {}, if the array is empty, it indicates that it cannot be repeated. true is returned.
3. for (var j = 0; j <arr. length; j ++) {}. If the array is not empty, the system traverses the elements in the array and compares them. If there are no duplicates, the system returns true. Otherwise, the system returns false. 4. var arr = [0, 1, 2, 3, 4, 5, 6, "a", "B", "c", "d", "e", "f ", "g"], to obtain the random number array, of course, can be expanded.
5. (function () {}) (arr), an self-executed function, and passing a parameter.
6. var randNum = null: declare a variable and assign the initial value to null to store randomly generated array indexes.
7. var old = [], create an empty array to store the existing array index values.
8. var str = "", creates an empty string to store the generated random number.
9. function done () {}, which can be used to obtain a random number.
10. randNum = Math. floor (Math. random () * 14) to obtain the index value of the array.
11. if (only (randNum, old )){
Str = str + arr [randNum];
Old. push (randNum );
} To determine whether it has been used. If not, obtain the array element, append it to the str string, and append the index value to the old array.
12. else {done ();
}, If you have already used it, obtain it again. Here we use recursion.
13. for (var index = 0; index <4; index ++ ){
Done ();
}, Use the for loop to obtain four random numbers.

From: http://www.softwhy.com/forum.php? Mod = viewthread & tid = 16493.