JavaScript Number object
Introduction
Number object is a numerical object, including integers, floating point numbers, etc. in js.
Definition
var a = 1;
var b = 1.1;
Attribute
##1 Number.MAX_VALUE: Represents the largest value in JS Number, approximately 1.79e+3082 Number.MIN_VALUE: Represents the smallest number in JS, approximately 5e-3243 Number.NaN: Returns NaN, indicating a non-numeric value, Not equal to any other number, including NaN itself. Number.isNaN() should be used to judge. 4 Number.NEGATIVE_INFINITY: Returns -Infinity, indicating negative infinity. 5 Number.POSITIVE_INFINITY: Returns Infinity, indicating positive infinity. If the calculated value is greater than Number.MAX_VALUE, Infinity is returned.
Method
##1 Number.isInteger(value): Determine whether the parameter is an integer
Parameters:
①value {Number}: number
Return value:
{Boolean} Returns whether the parameter is an integer. Pure integer strings also return false.
Example:
Number.isInteger(1); // => true
Number.isInteger(1.1); // => false
Number.isInteger('1'); // => false: Pure integer strings also return false
Number.isInteger('1.1'); // => false
Number.isInteger('a'); // => false: non-string returns false
2 Number.isNaN(value): determines whether the parameter is NaN
parameter :
①value {Object} : Any type
Return value:
{Boolean} Whether the return parameter is NaN.
Example:
Number.isNaN(NaN); // => true
Number.isNaN('NaN'); // => false :' NaN' string is not NaN
Number.isNaN(1); // => false
Number.isNaN('1'); // => false
3 Number.parseFloat(value): Convert the parameter to a floating point number
Parameters:
①value {Number | NumberStr}: Number or pure numeric string
return value:
{Integer | Float} Returns an integer or floating point number
Example:
Number.parseFloat(1); // => 1: Integer or returns an integer
Number.parseFloat(1.1); // => 1.1
Number.parseFloat('1aaa'); // => 1: If the string is preceded by a number, only numbers are returned
Number.parseFloat('1.1aaa'); // => 1.1
Number.parseFloat('a1'); // => NaN: does not start with a number, returns NaN
Number.parseFloat('a'); // => NaN
4 Number.parseInt(value): Convert the parameter to an integer
Parameter:
①value {Number | NumberStr}: Number or pure numeric string
Return value:
{Integer} Return integer value
Example:
Number.parseInt(1); // => 1
Number.parseInt(1.1); // => 1: Floating point number returns integer
Number.parseInt('1aaa' ); // => 1: If the string is preceded by a number, only numbers are returned
Number.parseInt('1.1aaa'); // => 1
Number.parseInt ('a1'); // => NaN: does not start with a number, returns NaN
Number.parseInt('a'); // => NaN
Octal and Hexadecimal
If the prefix is ??0, JavaScript will interpret the numeric constant as an octal number. If the prefix is ??0 and "x", it will be interpreted as a hexadecimal number. .
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>php中文網(wǎng)(php.cn)</title> </head> <body> <script> var y = 0377; var z = 0xFF; document.write(y + "<br>"); document.write(z + "<br>"); </script> </body> </html>
By default, JavaScript numbers are displayed in decimal.
But you can use the toString() method to output hexadecimal, octal, or binary.
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>php中文網(wǎng)(php.cn)</title> </head> <body> <script> var myNumber = 28; document.write(myNumber + ' 十進(jìn)制<br>'); document.write(myNumber.toString(16) + ' 十六進(jìn)制<br>'); document.write(myNumber.toString(8) + ' 八進(jìn)制<br>'); document.write(myNumber.toString(2) + ' 二進(jìn)制<br>'); </script> </body> </html>
Infinity
When the numerical operation result exceeds the upper limit of the number that JavaScript can represent (overflow), the result is a special infinity value, which is represented by Infinity in JavaScript express. Similarly, when the value of a negative number exceeds the range of negative numbers that JavaScript can represent, the result is negative infinity, which is represented by -Infinity in JavaScript. Infinite values ??behave as we would expect: operations based on their addition, subtraction, multiplication, and division still result in infinity (while retaining their signs, of course).
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<script>
myNumber=2;
while (myNumber!=Infinity){
myNumber=myNumber*myNumber;
document.write(myNumber +'<BR>');
}
</script>
</body>
</html>Number attributes
MAX_VALUE
MIN_VALUE
NEGATIVE_INFINITY
POSITIVE_INFINITY
NaN
prototype
constructor
數(shù)字方法
toExponential()
toFixed()
toPrecision()
toString()
valueOf()
