Question

我需要查看输入文本..如果是数字或任何其他字符..
要求是..它应该是正确的格式..并且不应包含除十进制数之外的任何其他字符？

我可以使用哪些内置功能来实现它？

如果有相同的重复帖子，请告诉我，我搜索但无法获得任何类似的重要帖子。

Answer 1

您可以使用数字功能：

    var num = Number(textValue);
    if (isNaN(num)) {
        // it's not a number
    }

请注意，转换为数字时，使用parseFloat 不会正常工作，因为parseFloat只会解析它找到的第一个数字。因此，如果您有一个像“4..5”这样的值，那么parseFloat将成功解析“4..5”并返回4作为数字，这是错误的。所以我们改用Number(value)。

Answer 2

来自spec：

11.4.6一元+运算符一元+运算符将其操作数转换为数字类型   制作

UnaryExpression：+ UnaryExpression是

评估如下：


让expr成为评估UnaryExpression的结果。

返回ToNumber（GetValue（expr））。

因此，调用+number将返回number表达式，无论是字符串还是其他内容。如果您不信任toNumber那么。请相信我能做到你想做的事。

来自规范：

9.3 ToNumber 
The abstract operation ToNumber converts its argument to a value of type Number according to Table 12: 
© Ecma International 2009 43Table 12 — To Number Conversions 
Argument Type  Result 
Undefined  NaN
Null  +0
Boolean  The result is 1 if the argument is  true. The result is +0 if the argument is 
false. 
Number  The result equals the input argument (no conversion). 
String  See grammar and note below. 
Object  Apply the following steps: 
1. Let primValue be ToPrimitive(input argument, hint Number). 
2. Return ToNumber(primValue).
9.3.1 ToNumber Applied to the String Type 
ToNumber applied to Strings applies the following grammar to the input String. If the grammar cannot interpret 
the String as an expansion of StringNumericLiteral, then the result of ToNumber is NaN. 
StringNumericLiteral :::
StrWhiteSpaceopt
StrWhiteSpaceopt
 StrNumericLiteral StrWhiteSpaceopt
StrWhiteSpace :::
StrWhiteSpaceChar StrWhiteSpaceopt
StrWhiteSpaceChar :::
WhiteSpace 
LineTerminator 
StrNumericLiteral :::
StrDecimalLiteral 
HexIntegerLiteral 
StrDecimalLiteral :::
StrUnsignedDecimalLiteral 
+ StrUnsignedDecimalLiteral 
- StrUnsignedDecimalLiteral 
StrUnsignedDecimalLiteral :::
Infinity
 DecimalDigits . DecimalDigitsopt ExponentPartopt
DecimalDigits ExponentPartopt .
DecimalDigits ExponentPartopt
DecimalDigits :::
DecimalDigit 
DecimalDigits DecimalDigit 
DecimalDigit ::: one of
0  1  2  3  4  5  6  7  8  9 
ExponentPart :::
ExponentIndicator SignedInteger 
ExponentIndicator ::: one of
e  E 
44  © Ecma International 2009SignedInteger :::
DecimalDigits 
+ DecimalDigits 
- DecimalDigits 
HexIntegerLiteral :::
0x HexDigit 
0X HexDigit 
HexIntegerLiteral HexDigit 
HexDigit ::: one of
0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  A  B  C  D  E  F 
Some differences should be noted between the syntax of a  StringNumericLiteral and a  NumericLiteral (see 
7.8.3): 
• A StringNumericLiteral may be preceded and/or followed by white space and/or line terminators. 
• A StringNumericLiteral that is decimal may have any number of leading 0 digits. 
• A StringNumericLiteral that is decimal may be preceded by + or - to indicate its sign. 
• A StringNumericLiteral that is empty or contains only white space is converted to +0. 
The conversion of a String to a Number value is similar overall to the determination of the Number value for a 
numeric literal (see 7.8.3), but some of the details are different, so the process for converting a String numeric 
literal to a value of Number type is given here in  full. This value is determined in two steps: first, a 
mathematical value (MV) is derived from the String numeric literal; second, this mathematical value is rounded 
as described below. 
• The MV of StringNumericLiteral ::: [empty] is 0. 
• The MV of StringNumericLiteral ::: StrWhiteSpace is 0. 
• The MV of  StringNumericLiteral ::: StrWhiteSpaceopt StrNumericLiteral StrWhiteSpaceopt
 is the MV of 
StrNumericLiteral, no matter whether white space is present or not. 
• The MV of StrNumericLiteral ::: StrDecimalLiteral is the MV of StrDecimalLiteral. 
• The MV of StrNumericLiteral ::: HexIntegerLiteral is the MV of HexIntegerLiteral. 
• The MV of StrDecimalLiteral ::: StrUnsignedDecimalLiteral is the MV of StrUnsignedDecimalLiteral. 
• The MV of StrDecimalLiteral ::: + StrUnsignedDecimalLiteral is the MV of StrUnsignedDecimalLiteral. 
• The MV of  StrDecimalLiteral ::: - StrUnsignedDecimalLiteral is the negative of the MV of 
StrUnsignedDecimalLiteral. (Note that if the MV of StrUnsignedDecimalLiteral is 0, the negative of this MV is 
also 0. The rounding rule described below handles the conversion of this signless mathematical zero to a 
floating-point +0 or −0 as appropriate.) 
• The MV of StrUnsignedDecimalLiteral::: Infinity is 10
10000
 (a value so large that it will round to +∞). 
• The MV of StrUnsignedDecimalLiteral::: DecimalDigits. is the MV of DecimalDigits. 
• The MV of StrUnsignedDecimalLiteral::: DecimalDigits . DecimalDigits is the MV of the first DecimalDigits
plus (the MV of the second DecimalDigits times 10
−n
), where n is the number of characters in the second 
DecimalDigits. 
• The MV of  StrUnsignedDecimalLiteral::: DecimalDigits. ExponentPart  is the MV of DecimalDigits times 10
e
 ,
where e is the MV of ExponentPart. 
• The MV of  StrUnsignedDecimalLiteral:::  DecimalDigits. DecimalDigits ExponentPart  is (the MV of the first 
DecimalDigits plus (the MV of the second DecimalDigits times 10
−n
)) times 10
e
, where n is the number of characters 
in the second DecimalDigits and e is the MV of ExponentPart. 
• The MV of StrUnsignedDecimalLiteral:::. DecimalDigits is the MV of DecimalDigits times 10
−n
, where n is the 
number of characters in DecimalDigits. 
• The MV of StrUnsignedDecimalLiteral:::. DecimalDigits ExponentPart  is the MV of DecimalDigits times 10
e−n
 ,
where n is the number of characters in DecimalDigits and e is the MV of ExponentPart. 
• The MV of StrUnsignedDecimalLiteral::: DecimalDigits is the MV of DecimalDigits. 
• The MV of  StrUnsignedDecimalLiteral:::  DecimalDigits ExponentPart  is the MV of  DecimalDigits times 10
e
 ,
where e is the MV of ExponentPart. 
• The MV of DecimalDigits ::: DecimalDigit is the MV of DecimalDigit. 
© Ecma International 2009 45• The MV of DecimalDigits ::: DecimalDigits DecimalDigit is (the MV of DecimalDigits times 10) plus the MV of 
DecimalDigit. 
• The MV of ExponentPart ::: ExponentIndicator SignedInteger is the MV of SignedInteger. 
• The MV of SignedInteger ::: DecimalDigits is the MV of DecimalDigits. 
• The MV of SignedInteger ::: + DecimalDigits is the MV of DecimalDigits. 
• The MV of SignedInteger ::: - DecimalDigits is the negative of the MV of DecimalDigits. 
• The MV of DecimalDigit ::: 0 or of HexDigit ::: 0 is 0. 
• The MV of DecimalDigit ::: 1 or of HexDigit ::: 1 is 1. 
• The MV of DecimalDigit ::: 2 or of HexDigit ::: 2 is 2. 
• The MV of DecimalDigit ::: 3 or of HexDigit ::: 3 is 3. 
• The MV of DecimalDigit ::: 4 or of HexDigit ::: 4 is 4. 
• The MV of DecimalDigit ::: 5 or of HexDigit ::: 5 is 5. 
• The MV of DecimalDigit ::: 6 or of HexDigit ::: 6 is 6. 
•     The MV of DecimalDigit ::: 7 or of HexDigit ::: 7 is 7. 
• The MV of DecimalDigit ::: 8 or of HexDigit ::: 8 is 8. 
• The MV of DecimalDigit ::: 9 or of HexDigit ::: 9 is 9. 
• The MV of HexDigit ::: a or of HexDigit ::: A is 10. 
• The MV of HexDigit ::: b or of HexDigit ::: B is 11. 
• The MV of HexDigit ::: c or of HexDigit ::: C is 12. 
• The MV of HexDigit ::: d or of HexDigit ::: D is 13. 
• The MV of HexDigit ::: e or of HexDigit ::: E is 14. 
• The MV of HexDigit ::: f or of HexDigit ::: F is 15. 
• The MV of HexIntegerLiteral ::: 0x HexDigit is the MV of HexDigit. 
• The MV of HexIntegerLiteral ::: 0X HexDigit is the MV of HexDigit. 
• The MV of HexIntegerLiteral  ::: HexIntegerLiteral HexDigit is (the MV of HexIntegerLiteral times 16) plus the 
MV of HexDigit. 
Once the exact MV for a String numeric literal has  been determined, it is then rounded to a value of the 
Number type. If the MV is 0, then the rounded value is +0 unless the first non white space character in the 
String numeric literal is ‘-’, in which case the rounded value is −0. Otherwise, the rounded value must be the 
Number value for the MV (in the sense defined in 8.5), unless the literal includes a StrUnsignedDecimalLiteral
and the literal has more than 20 significant digits, in which case the Number value may be either the Number 
value for the MV of a literal produced by replacing each significant digit after the 20th with a 0 digit or the 
Number value for the MV of a literal produced by replacing each significant digit after the 20th with a 0 digit 
and then incrementing the literal at the 20th digit position. A digit is significant if it is not part of an ExponentPart
and 
• it is not 0; or 
• there is a nonzero digit to its left and there is a nonzero digit, not in the ExponentPart, to its right.

Answer 3

另外如果想自己解析字符串，可以使用描述的String方法 here。

检查字符串的内容，无论是数字还是其他字符？

3 个答案: