Regular expression to test whether a string consists of a valid real number in base 10

"1"     yes
"-1"    yes
"- 3"   no
"1.2"   yes
"1.2.3" no
"7e4"   no  (though in some cases you may want to allow scientific notation)
".123"  yes
"123."  yes
"."     no
"-.5"   yes
"007"   yes
"00"    yes

/^s*[+-]?(?:d+.?d*|d*.d+)s*$/

/^[-+]?(?=.?d)d*(?:.d*)?$/

/^[-+]?(?:.d+|d+(?:.d*)?)$/
/^[-+]?(.d+|d+(.d*)?)$/ # if you don't mind capturing parens

/^[-+]?(?:.d+|(?:0|[1-9]d*)(?:.d*)?)$/
/^[-+]?(.d+|(0|[1-9]d*)(.d*)?)$/

/^[-+]?(?:.[0-9]+|(?:0|[1-9][0-9]*)(?:.[0-9]*)?)$/
/^[-+]?(.[0-9]+|(0|[1-9][0-9]*)(.[0-9]*)?)$/

^[+-]?(?:d+(?:.d*)?|.d+)$

^[+-]?(?:d+(?:.d+)?|.d+)$

d*

/^s*[-+]?(d+|d*.d+)s*$/