1. Math Object
1.1 Introduction
The Math object, which is a mathematical object, provides a mathematical calculation of the data, such as acquiring absolute value, rounding up, and so on. No constructors, cannot be initialized, provides only static properties and methods.
1.2 Constructors
None: The Math object has no constructors, cannot be initialized, and provides only static properties and methods.
1.3 Static properties
1.3.1 MATH.E: Constant E. Returns the base of the natural logarithm: 2.718281828459045
1.3.2 Math.PI: Constant π. return value of pi: 3.141592653589793
1.4 Static Methods
1.4.1 Math.sin (value): sine function
1.4.2 Math.Cos (value): cosine function
1.4.3 Math.tan (value): Tangent function
1.4.4 Math.asin (value): Inverse chord function
1.4.5 Math.acos (value): Anti-cosine function
1.4.6 Math.atan (value): Inverse tangent function
1.4.7 Math.Abs (value): Returning absolute value
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{Number} returns the absolute value of the parameter. Returns Nan If the argument is not a number.
Example:
Copy Code code as follows:
H.abs (' 123 '); => 123: Pure numeric string
Math.Abs ('-123 '); => 123
Math.Abs (123); => 123
Math.Abs (-123); => 123
Math.Abs (' 123a '); => NaN: Non-pure numeric string
1.4.8 Math.ceil (value): Rounding a number up, not rounded
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{Number} returns the value after rounding. Returns Nan If the argument is not a number.
Example:
Copy Code code as follows:
Math.ceil (2.7); => 3
Math.ceil (2.3); => 3:2.3 up, rounding back 3.
Math.ceil (-2.7); =>-2
Math.ceil (-2.3); =>-2
Math.ceil (' 2.7 '); => 3: Pure numeric string
Math.ceil (' 2.7a '); => NaN: Non-pure numeric string
1.4.9 Math.floor (value): Rounding a number down, not rounded
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{Number} returns the value after rounding. Returns Nan If the argument is not a number.
Example:
Copy Code code as follows:
Math.floor (2.7); => 2
Math.floor (2.3); => 2
Math.floor (-2.7); =>-3:-2.7 down-rounding return-3
Math.floor (-2.3); =>-3
Math.floor (' 2.7 '); => 2: Pure numeric string
Math.floor (' 2.7a '); => NaN: Non-pure numeric string
1.4.10 Math.max (Value1,value2...valuen): Returns the largest value in a parameter
Parameters:
①value1,value2.....valuen {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{Number} returns the maximum value. If a parameter is not a number, return Nan.
Example:
Copy Code code as follows:
Math.max (1, 2, 3, 4, 5); => 5
Math.max (1, 2, 3, 4, ' 5 '); => 5
Math.max (1, 2, 3, 4, ' a '); => NaN
1.4.11 math.min (Value1,value2...valuen): Returns the smallest value in a parameter
Parameters:
①value1,value2.....valuen {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{Number} returns the maximum value. If a parameter is not a number, return Nan.
Example:
Copy Code code as follows:
Math.min (1, 2, 3, 4, 5); => 1
Math.min (' 1 ', 2, 3, 4, 5); => 1
Math.min (1, 2, 3, 4, ' a '); => NaN
1.4.12 Math.pow (X,y): Returns the Y-side of X
Parameters:
①x {Number | NUMBERSTR}: A string of numbers or plain numbers.
②y {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{Number} returns the Y-second side of X. If a parameter is not a number, return Nan.
Example:
Copy Code code as follows:
Math.pow (2, 3); => 8:2 of the 3-time party
Math.pow (3, 2); => 9:3 of the 2-time party
Math.pow (' 4 ', 2); => 16:4 of the 2-time party
Math.pow (' 2a ', 2); => NaN
1.4.13 math.random (): Returns a pseudo random number, greater than 0, less than 1.0
Parameters: None
return value:
{Number} returns a pseudo random count of more than 0, less than 1.0
Example:
Copy Code code as follows:
Math.random (); => 0.8982374747283757
Math.random (); => 0.39617531932890415
Math.random (); => 0.35413061641156673
Math.random (); => 0.054441051790490746
1.4.14 Math.Round (value): Rounded after rounding
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers.
return value:
{integer} returns an integer after the parameter is rounded. Returns Nan If the argument is not a number.
Example:
Copy Code code as follows:
Math.Round (2.5); => 3
Math.Round (2.4); => 2
Math.Round (-2.6); =>-3
Math.Round (-2.5); =>-2:-2.5 rounded to-2
Math.Round (-2.4); =>-2
Math.Round (' 2.7 '); => 3: Pure numeric string
Math.Round (' 2.7a '); => NaN: Non-pure numeric string
1.4.15 math.sqrt (value): Returns the square root of a parameter
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers
return value:
{Number} returns the square root of the parameter
Example:
Copy Code code as follows:
Console.log (MATH.SQRT (9)); => 3
Console.log (MATH.SQRT (16)); => 4
Console.log (math.sqrt (' 25 ')); => 5
Console.log (Math.sqrt (' a ')); => NaN
2. Number Object
2.1 Introduction
Number object is a numeric object that contains integers, floating-point numbers, and so on in JS.
2.2 Definition
Copy Code code as follows:
2.3 Static Properties
2.3.1 Number.MAX_VALUE: Represents the largest number in JS, about 1.79e+308
2.3.2 Number.min_value: Represents the smallest number in JS, about 5e-324
2.3.3 Number.NaN: Returns Nan, indicating non-numeric values, which range from any other number, including the Nan itself. The Number.isnan () should be used for judgment.
2.3.4 number.negative_infinity: Returns-infinity, representing negative infinity.
2.3.5 number.positive_infinity: Returns INFINITY, representing positive infinity. Returns Infinity if the value being calculated is greater than number.max_value.
2.4 Static methods
2.4.1 Number.isinteger (value): Determining whether an argument is an integer
Parameters:
①value {Number}: Digital
return value:
{Boolean} returns whether the argument is an integer. The string of a pure integer also returns false.
Example:
Copy Code code as follows:
Number.isinteger (1); => true
Number.isinteger (1.1); => false
Number.isinteger (' 1 '); => false: string of pure integers also returns false
Number.isinteger (' 1.1 '); => false
Number.isinteger (' a '); => false: Non-string return false
2.4.2 Number.isnan (value): Determines whether the parameter is Nan
Parameters:
①value {Object}: any type
return value:
{Boolean} returns whether the parameter is Nan.
Example:
Copy Code code as follows:
Number.isnan (NaN); => true
Number.isnan (' NaN '); => false: ' Nan ' string, not Nan
Number.isnan (1); => false
Number.isnan (' 1 '); => false
2.4.3 Number.parsefloat (value): Converting parameters to floating point numbers
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers
return value:
{Integer | FLOAT} returns an integer or floating-point number
Example:
Copy Code code as follows:
Number.parsefloat (1); => 1: integer or return integer
Number.parsefloat (1.1); => 1.1
Number.parsefloat (' 1aaa '); => 1: The string is preceded by a number, and only the number is returned
Number.parsefloat (' 1.1aaa '); => 1.1
Number.parsefloat (' A1 '); => nan: Not beginning with a number, returning Nan
Number.parsefloat (' a '); => NaN
2.4.4 Number.parseint (value): Converts a parameter to an integer
Parameters:
①value {Number | NUMBERSTR}: A string of numbers or plain numbers
return value:
{integer} returns an integer value
Example:
Copy Code code as follows:
Number.parseint (1); => 1
Number.parseint (1.1); => 1: Floating-point numbers return integers
Number.parseint (' 1aaa '); => 1: The string is preceded by a number, and only the number is returned
Number.parseint (' 1.1aaa '); => 1
Number.parseint (' A1 '); => nan: Not beginning with a number, returning Nan
Number.parseint (' a '); => NaN
2.5 Instance Methods
2.5.1 toexponential (value): Converts a number to an exponential type, with a parameter representing the number of digits after the decimal point
Parameters:
①value {Number}: Indicates digits after the decimal point
return value:
{string} returns the converted exponential type string
Example:
Copy Code code as follows:
(123456789). toexponential (2); => 1.23e+8:2 decimal places
(123456789). toexponential (5); => 1.23457e+8:5 decimal places
(123456789). toexponential (10); => 1.2345678900e+8: The decimal point 10 digits, the number of insufficient digits with 0 complement
2.5.2 toFixed (value): Converts a number to a string that specifies the number of decimal places. Without passing in the argument, there is no decimal digit. The return value is rounded
Parameters:
①value {Number}: Indicates digits after the decimal point
return value:
{string} returns the converted string; not enough decimal places to fill with 0; The return value is rounded
Example:
Copy Code code as follows:
Console.log ((1). toFixed (2)); => 1.00
Console.log ((1.2). ToFixed (2)); => 1.20: Insufficient digits, with 0 complement
Console.log ((1.277). toFixed (2)); => 1.28: Rounded up
2.5.3 toString (): Converts a number to a string using the specified system. No parameters are passed in, and the default is decimal.
Parameters:
①value {Number}: Represents the numbers, values range: 2 to 36
return value:
{string} converts a backward string
Example:
Copy Code code as follows:
(a). ToString (); => 10: The default is decimal
(a). ToString (2); => 1010: Binary
(a). ToString (10); => 10: Decimal
(a). ToString (16); => A: Hex
2.6 Application Scenarios
Subtraction anomaly of 2.6.1 floating-point numbers
Note: JS 2 floating-point numbers in the subtraction operation, will return the value of the exception, such as: 0.2+0.7, returned 0.899999999999. You can use the tofixed () method to specify a decimal place.
Example:
Copy Code code as follows:
Console.log (0.2 + 0.7); => 0.8999999999999999
Console.log (0.7-0.5); => 0.19999999999999996
Console.log (3.03 * 10); => 30.299999999999997
Using the Tofixed () method
Console.log ((0.2 + 0.7). ToFixed (2)); => 0.90
Console.log ((0.7-0.5). toFixed (2)); => 0.20
Console.log ((3.03 *). ToFixed (2)); => 30.30
2.6.2 Subtraction Operation
Note: JS in the subtraction operation, will first the value before and after conversion to the number and then operation. If the conversion fails, return Nan.
Example:
Copy Code code as follows:
Console.log (' 1 '-0); => 1: Pure numeric string minus 0, can be quickly converted to Nubmer object
Console.log (' 1 '-0). toFixed (2)); => 1.00: Invoke instance method after fast conversion to Nubmer object
Console.log (' 1 '-' a '); => NaN: One side cannot be converted to a Nubmer object
