How does JS determine whether the input is a positive integer, floating-point number, and other numeric functions?

How does JS determine whether the input is a positive integer, floating point number, and other numeric Functions

1. The following lists some regular expressions that interpret numeric types. "^ // D + $" // non-negative integer (positive integer + 0) "^ [0-9] * [1-9] [0-9] * $" // positive integer "^ (-// D +) | (0 +) $" // non-positive integer (negative integer + 0) "^-[0-9] * [1-9] [0-9] * $" // negative integer "^ -? // D + $ "// integer "^/D + (//. // D + )? $ "// Non-negative floating point number (Positive floating point number + 0) "^ ([0-9] + //. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * //. [0-9] +) | ([0-9] * [1-9] [0-9] *) $ "// Positive floating point number "^ (-/D + (//. // D + )?) | (0 + (//. 0 + )?)) $ "// Non-Positive floating point number (negative floating point number + 0) "^ (-([0-9] + //. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * //. [0-9] +) | ([0-9] * [1-9] [0-9] *) $ "// negative floating point number "^ (-? // D +) (//. // D + )? $ "// Floating point number 2. usage in the program VaR r =/^ [0-9] * [1-9] [0-9] * $ // positive integer R. Test (STR); // STR returns true or false for the characters to be judged. 3. Test a regular expression function, which can be used to determine the JS function of the number character date email. Function testrgexp (Re, S) {// parameter description Re is the regular expression s is the character to be judged Return re. test (s) } 4. function applications Function testrgexp (Re, S) {// parameter description Re is the regular expression s is the character to be judged Return re. test (s) } VaR Re =/^ [0-9] * [1-9] [0-9] * $ /; // Determine whether the expression is a positive integer. Note: Regular Expression format in the program:/the regular expression above (without double quotation marks )/ VaR S = prompt ("Enter the character to be judged", 10 ); VaR result = testrgexp (Re, S); // return true or false for the test Alert (result );   5. Example HTML code       <Script. type = "text/JavaScript"> Function testrgexp (Re, S) {// parameter description Re is the regular expression s is the character to be judged Return re. test (s) } VaR Re =/^ [0-9] * [1-9] [0-9] * $ /; // Determine whether it is a positive integer <span style = "color: Red"> Note: Regular Expression format in the program:/the regular expression above (without double quotation marks)/</span> VaR S = prompt ("Enter the character to be judged", 10 ); VaR result = testrgexp (Re, S); // return true or false for the test <SCRIPT> Function A (string_value) { VaR type = "^/S * [+-]? [0-9] +/S * $ "; VaR Re = new Regexp (type ); If (string_value.match (re) = NULL) { Alert ("not an integer "); } Else { Alert ("is an integer "); } } </SCRIPT> <Input name = "B" value = ""> <Input type = "button" value = "test" onclick = "A (document. All. B. Value)">