Things to note about the Math() function in javaScript

Things to note about the Math() function in javaScript_javascript tips

WBOY

Release： 2016-05-16 15:54:18

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1. You cannot create a Math object explicitly, just use it directly;

2.Math objects cannot store data, unlike String and Date objects;

3. As we know earlier, the parseInt() function will turn a decimal into an integer by eliminating everything after the decimal point (so 24.999 becomes 24). Often we need more accurate calculations.

So through these methods of the Math object:

round(): When the decimal is 0.5 or greater than 0.5, add one digit upward;

ceil(): always rounds up, so 23.75 becomes 24, and the same goes for 23.25;

floor(): always rounds down, so 23.75 becomes 23, and the same goes for 23.25;

<DOCTYPE html>
<html>
  <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
  <head>
    <title>Math函数</title>
  </head>
  <script type="text/javascript">
    var userInput=prompt("请输入一个数","");
    document.write("round()=",+Math.round(userInput));
    document.write("ceil()=",+Math.ceil(userInput));
    document.write("floor()=",+Math.floor(userInput));
    
  </script>
  <body>
  </body>
</html>

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4. You can use the random() method of the Math object to generate a random decimal number greater than or equal to 0 but less than 1. Usually to take advantage of this, you need to multiply by some number and then use one of the rounding methods.

var diceThrow=Math.round(Math.random()*6)+1;
document.write("You threw a "+diceThrow);

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Attach the method of Math object

1. Discard the decimal part and keep the integer part
parseInt(5/2)
2. Round up, if there is a decimal, add 1 to the integer part
Math.ceil(5/2)
3, Rounded.
Math.round(5/2)
4. Round down
Math.floor(5/2)
Methods of Math object
FF: Firefox, N: Netscape, IE: Internet Explorer
Method Description FF N IE
abs(x) returns the absolute value of the number 1 2 3
acos(x) returns the arc cosine of the number 1 2 3
asin(x) returns the arcsine of the number 1 2 3
atan(x) returns the arctangent of x as a number between -PI/2 and PI/2 radians 1 2 3
atan2(y,x) returns the angle from the x-axis to the point (x,y) (between -PI/2 and PI/2 radians) 1 2 3
ceil(x) rounds a number up. 1 2 3
cos(x) returns the cosine of the number 1 2 3
exp(x) returns the exponent of e. 1 2 3
floor(x) rounds a number down. 1 2 3
log(x) returns the natural logarithm of the number (base is e) 1 2 3
max(x,y) returns the highest value between x and y 1 2 3
min(x,y) returns the lowest value between x and y 1 2 3
pow(x,y) returns x raised to the y power 1 2 3
random() returns a random number between 0 ~ 1 1 2 3
round(x) rounds a number to the nearest integer 1 2 3
sin(x) returns the sine of the number 1 2 3
sqrt(x) returns the square root of the number 1 2 3
tan(x) returns the tangent of an angle 1 2 3
toSource() represents the source code of the object 1 4 -
valueOf() returns the original value of a Math object

1. Math.abs(num): Returns the absolute value of num
2. Math.acos(num): Returns the arc cosine value of num
3. Math.asin(num): Returns the arcsine value of num
4. Math.atan(num): Returns the arctangent value of num
5. Math.atan2(y,x): Returns the arc tangent of the quotient of y divided by x
6. Math.ceil(num): Returns the smallest integer greater than num
7. Math.cos(num): Returns the cosine value of num
8. Math.exp(x): Returns a number raised to the power of x with a natural number as the base
9. Math.floor(num): Returns the largest integer less than num
10.Math.log(num): Returns the natural logarithm of num
11.Math.max(num1,num2): Returns the larger of num1 and num2
12.Math.min(num1,num2): Returns the smaller of num1 and num2
13.Math.pow(x,y): Returns the value of x raised to the power of y
14.Math.random(): Returns a random number between 0 and 1
15.Math.round(num): Returns the rounded value of num
16.Math.sin(num): Returns the sine value of num
17.Math.sqrt(num): Returns the square root of num
18.Math.tan(num): Returns the tangent value of num
19.Math.E: Natural numbers (2.718281828459045)
20.Math.LN2: Natural logarithm of 2 (0.6931471805599453)
21.Math.LN10: Natural logarithm of 10 (2.302585092994046)
22.Math.LOG2E: The natural number with base log 2 (1.4426950408889634)
23.Math.LOG10E: log 10 base natural number (0.4342944819032518)
24.Math.PI: π(3.141592653589793)
25.Math.SQRT1_2: The square root of 1/2 (0.7071067811865476)
26.Math.SQRT2: The square root of 2 (1.4142135623730951)

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