What is the usage of math.random() in javascript

math.random() in javascript is used to generate random numbers. Its usage syntax is such as "Math.floor(Math.random() * 10 1);". This statement can be used in continuous integers. Get a random number.

The operating environment of this article: windows7 system, javascript version 1.8.5, DELL G3 computer

Use of Math.random() in javascript Detailed explanation

Math.random() I believe everyone knows that this method is used to generate random numbers. However, the general reference manual does not explain how to use this method to generate random numbers within a specified range. This time I will introduce Math.random() in detail and how to use it to generate random numbers within a specified range.

The Math.random() method returns a random number greater than or equal to 0 and less than 1. For some sites, this method is very practical, because it can be used to randomly display some famous quotes and news events.

1. Obtain a random number from a continuous integer

Value = Math.floor(Math.random() * the first possible value of the total number of possible values)

Example: Generate random numbers from 1 to 10

The code is as follows:

var rand1 = Math.floor(Math.random() * 10 + 1);

Write a function that generates random numbers from startNumber to endNumber

The code is as follows:

function selectFrom(startNumber, endNumber) {
    var choice = endNumber - startNumber + 1;
    return Math.floor(Math.random() * choice + startNumber)
}
var rand2 = selectFrom(2,8);//产生2至8的随机数

2. Obtain a random number from non-adjacent integers

2.1 Obtain a random number from two non-adjacent integers

Example: Randomly generate a number between 2 or 4

The code is as follows:

var rand3 = Math.random() < 0.5 ? 2 : 4;

2.2 Generate a random number from multiple non-adjacent integers

Combined with the function parameter array, it can be written in multiple non-adjacent integers The function

that generates a random value from an integer has the following code:

function selectFromMess() {
    return arguments[Math.floor(Math.random() * arguments.length)]
}
//随机产生1、6、8中的一个数
var rand4 = selectFromMess(1, 6, 8);
//也可随机产生文本
var randomTxt1 = selectFromMess("安慰奖", "二等奖", "一等奖");

It is troublesome to enter so many parameters every time. You can rewrite the function

and the code is as follows:

function selectFromMessArray(arr) {
    return arr[Math.floor(Math.random() * arr.length)]
}
var arrayTxt=["一","二","三","四","五"];
var randTxt2 = selectFromMessArray(arrayTxt);

Or do not change the original method, you can use the apply() method to pass array parameters

Copy the code as follows:

var randTxt3 = selectFromMess.apply(null,arrayTxt);

Recommended study: "javascript basic tutorial》

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