JavaScript ?? ??
??
Number ??? js? ??, ?? ??? ?? ?? ???? ??? ?????.
Definition
attribute 1 Number.MAX_VALUE: JS?? ?? ? ??? ?????. ? 1.79e+308
2 Number.MIN_VALUE? ?????. ?? ?? ?? JS??? ? 5e-3243 Number.NaN: NaN ??? ???? ?? ??? ?? ?? ??? ?? ?? ???? NaN? ?????. Number.isNaN()? ???? ???? ???.
4 Number.NEGATIVE_INFINITY: ?? ???? ???? -Infinity? ?????.5 Number.POSITIVE_INFINITY: ?? ???? ???? ???? ?????. ??? ?? Number.MAX_VALUE?? ?? Infinity? ?????.
Method
1 Number.isInteger(value): ????? ???? ??????: ①value {Number}: Number???:{Boolean} ??? ?????. ????? Integer ???. ?? ?? ???? false? ?????.
?:Number.isInteger(1); // => true
Number.isInteger(1.1) // => falseNumber.isInteger('1'); false: ?? ?? ???? false? ?????Number.isInteger('1.1'); // => falseNumber.isInteger('a') // => false: ???? ?? ?? false 2 Number.isNaN(?): ????? NaN?? ??????: ①value {Object}: ?? ?????: {Boolean} ????? NaN?? ??? ?????. ?: Number.isNaN(NaN); // => trueNumber.isNaN('NaN') // => false: NaN? ?? 'NaN' ??? .isNaN( 1); // => falseNumber.isNaN('1'); // => false3 Number.parseFloat(value): ????? ?? ??? ??? ?????.①value {Number | NumberStr}: ?? ?? ?? ?? ????? ?:
{Integer | Float} ?? ?? ?? ??? ?? ?????.
?:
Number.parseFloat(1) // => 1: ?? ?? ??? ?????.
Number.parseFloat(1.1); > 1.1
Number.parseFloat('1aaa'); // => 1: ??? ?? ??? ??? ??? ?????.
Number.parseFloat('1.1aaa') // => ; 1.1
Number .parseFloat('a1'); // => NaN: NaN
Number.parseFloat('a') // => .parseInt(?): ????? ??? ??
????:
①? {Number | NumberStr}: ?? ?? ?? ?? ???
?? ?:
{Integer} ?? ? ??
?:
Number .parseInt(1); / / => 1
Number.parseInt(1.1); // => 1: ?? ??? ??? ??? ?????
Number.parseInt('1aaa'); ; 1: ??? ?? ??? ???. ??? ?????.
Number.parseInt('1.1aaa') // => 1
Number.parseInt('a1') // => ??? ?? ??, NaN
Number.parseInt ('a')? ?????. // => NaN
8?? ? 16??
???? 0? ?? JavaScript? ?? ??? 8??? ?????. ?????. ???? 0?? "x"? ?? 16??? ?????.
<!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>
????? JavaScript ??? ???? ?????.
??? toString() ???? ???? 16??, 8?? ?? 2??? ??? ? ????.
<!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
???? ??? ??????? ??? ? ?? ??? ??? ??(????)?? ??, ? ??? ???????? Infinity? ???? ??? ??? ?? ???. ?????, ??? ?? ??????? ??? ? ?? ??? ??? ???? ?? ??? ?? ?????, ?? ???????? -Infinity? ?????. ?? ?? ??? ??? ?? ?????. ??, ??, ??, ???? ???? ? ??? ??? ?????? ???(?? ??? ???).
<!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>?? ??
MAX_VALUE
MIN_VALUE
NEGATIVE_INFINITY
POSITIVE_INFINITY
NaN
prototype
constructor
toExponential()
toFixed()
toPrecision()
toString()
valueOf()
