The JS rounded up, rounding down, rounding, etc.

• Retaining only the integer part (decimal part is discarded)

parseInt(5.1234);      // 5

• Rounding down (largest integer <= the numerical value, and the parseInt () as)

Math.floor(5.1234);     // 5    

• Rounding up (with decimal integer part to +1)

Math.ceil(5.1234);     // 6

• Rounding (fractional part)

Math.round(5.1234);      // 5
Math.round(5.6789);     // 6

• Absolute value

Math.abs(-1);      // 1

• Returns the larger of two numbers

Math.max(1,2);     // 2

• Returns the smaller of two numbers

Math.min(1,2);    // 1

• Random Number (0-1)

Math.random();  //返回 0（包括） 至 1（不包括） 之间的随机数

JavaScript random integer

Used together Math.random () and Math.floor () returns a random integer.

Math.floor(Math.random() * 10);     // 返回 0 至 9 之间的数 

Math.floor(Math.random() * 11);     // 返回 0 至 10 之间的数

Math.floor(Math.random() * 100);    // 返回 0 至 99 之间的数

Math.floor(Math.random() * 101);    // 返回 0 至 100 之间的数

Math.floor(Math.random() * 10) + 1; // 返回 1 至 10 之间的数

Math.floor(Math.random() * 100) + 1;    // 返回 1 至 100 之间的数

An appropriate random function
As you can see from the above example, create a random function is used to generate all the random integer is a good idea.

This JavaScript function always returns a random number between min (including) and max (not included) between:

function getRndInteger(min, max) {
    return Math.floor(Math.random() * (max - min) ) + min;
}

This JavaScript function always returns a random number between min and max (both included) between:

function getRndInteger(min, max) {
    return Math.floor(Math.random() * (max - min + 1) ) + min;
}

Original: https://www.jianshu.com/p/a93bd02d9eb7