<>JavaScript study Lesson Two （ two ）
one ,Math object ：
This object is used to handle mathematical operators , The object does not need to be created manually , Because it is window Object , When the page is loaded , The background is created automatically Math object , It can be used window.Math Ali use . Or omit window object , Direct use Math.
two ,Math Common properties of —PI
1, effect ： Get pi
2, format ：Math.PI
three ,Math The common methods to solve this problem
1）,round method ：
effect ： Round the data
format ： Math.round( data );
Return value ： Returns the integer part of the data , That is to say, when rounding the data, the method is to process one digit after the decimal point .
console.log(Math.round(3.14));
2),ceil method ：
effect ： Round up the data , Take the smallest integer
format ：Math.ceil( data );
Return value ： The smallest integer larger than data
console.log(Math.ceil(3.74));
3）floor method ：
effect ： Round down the data , Take the largest integer
format ：Math.floor( data );
console.log(Math.floor(3.74));
4）,random method ：
effect ： generate 0-1 Random number of , contain 0, But not included 1
format ：Math.random();
be careful ：
1）： If you want to generate n-m, And include n and m Random integer of :
parseInt(Math.random()*( Maximum +1- minimum value )+ minimum value );
2)： If you want to generate random subscripts of arrays or strings ：
parseInt(Math.random() * array .length); console.log(Math.random());
5) ,max method ：
effect ; Finding the maximum value of a set of data
format ：Math.max( value 1, value 2, value 3…);
6),min method ：
effect ： Find the minimum value in a set of data
format ：Math.min( value 1, value 2, value 3…);
console.log(Math.min(1, 2, 4, 7, 10)); console.log(Math.max(10, 4, 5, 90));
7),abs method ：
effect ： Finding the absolute value of data
format ：Math.abs( value );
Return value ： Absolute value of data ;
console.log(Math.abs(-1));
8）,pow method
effect ： seek x Of y Power
format ：Math.pow(x,y);
console.log(Math.pow(2, 10));
9),sqrt method ：
effect ： Finding the arithmetic square root of data
format ：Math.sqrt( data );
console.log(Math.sqrt(4));
four ,toFixed method
effect ： To process the number of decimal places of a data
format ： data .toFixed( Number of decimal places );
be careful ： The return value of this method is a string type
var num = Math.PI; var res = num.toFixed(3); console.log(res); console.log(
typeof res);
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