JavaScript generates _JAVASCRIPT techniques for random numbers with no duplicates

Source: A test question in the process of learning jquery in Mu class.

Initially, only 5 <li> elements are displayed in the:<ul> element, which includes the display of "more" characters in the last <li> element,<a> element.

When you click on the "More" link, the content becomes "simplified" while the,<ul> element displays all the <li> elements.

When you click on the "Simplify" link, your content becomes "more", while the,<ul> element displays only 5 elements, including the last <li> element.

Core point: He didn't tell me what a few <li> elements to hide, so I wanted to list 8 <li> elements, and point to simplify the 3 of the first 7 <li> elements that were randomly hidden.

Ideas:

① generates 3 random numbers from the 0~6.

② to determine whether 3 random numbers are equal and unequal then perform a hidden operation.

③3 The random number has a duplicate, the function is executed again.

Implementation: Generates a random number of 0~6

Copy Code code as follows:

var ran1=parseint (Math.random () *7); Math.random () A random number that generates [0,1]

Complete code:

<! DOCTYPE html>  

Harvest One:

Copy Code code as follows:

var ran=parseint (Math.random () * (max-min+1) +min); Generates a random number for a [Min,max] interval

Harvest Two:

In retrospect, the decision to write a package function that generates n a random number of not duplicates in a certain [Min,max] interval.

Idea one: Sir into n [Min,max] interval random number, compare whether repeat, if repeat, return, execute again.

Demo Address: Http://jsbin.com/yupuyehuqa/edit?html,js,output

Encapsulate function:

function My_ran (N,min,max) {
 var arr=[];
 for (i=0;i<n;i++) {
  arr[i]=parseint (Math.random () * (max-min+1) +min);
 for (i=0;i<n;i++) {for
  (j=i+1;j<n;j++) {
   if (Arr[i]==arr[j]) {
    My_ran (N,min,max);
    return fault;
   }
  }
 return arr;
}

Idea two: Generate the random number of the first [Min,max] interval, and compare with the number of previous i-1, if there is repetition, make i=i-1, repeat generation I random number.

Demo Address: Http://jsbin.com/zorunotosi/edit?html,js,output

Encapsulate function:

function My_ran2 (N,min,max) {
 var arr=[];
 for (i=0;i<n;i++) {
  arr[i]=parseint (Math.random () * (max-min+1) +min);
  for (j=0;j<i;j++) {
   if (Arr[i]==arr[j]) {
    i=i-1;
    break;
   }
 }} return arr;
}

Idea three: Generate a sequential array of [min,max] intervals, disrupt the array, and output the first n values.

Demo Address: Http://jsbin.com/zorunotosi/edit?html,js,output

Encapsulate function:

function My_ran3 (N,min,max) {
 var arr=[];
 var arr2=[];
 for (i=0;i<max-min+1;i++) {
  arr[i]=i+min;
 }
 For (Var j,x,i=arr.length;i;j=parseint (Math.random () *i), x=arr[--i],arr[i]=arr[j],arr[j]=x);
 for (i=0;i<n;i++) {
  arr2[i]=arr[i];
 }
 return arr2;
}

Idea four: Generate a sequential array of [Min,max] intervals from which to randomly select a value, then delete the value in the array, and then select the second random value.

Demo Address: Http://jsbin.com/zorunotosi/edit?html,js,output

Encapsulate function:

function My_ran4 (N,min,max) {
 var arr=[];
 var arr2=[];
 for (i=0;i<max-min+1;i++) {
  arr[i]=i+min;
 }
 for (i=0;i<n;i++) {
  var x=parseint (Math.random () *arr.length);
  ARR2[I]=ARR[X];
  for (j=x;j<arr.length;j++) {
   arr[j]=arr[j+1];
  }
  arr.length=arr.length-1;
 }
 return arr2;
}

It's too late, tomorrow there is no time to adjust the format.

The above mentioned is the entire content of this article, I hope you can enjoy.