Parse source as an double literal and return its value.
Accepts an optional sign (+ or -) followed by either the characters
"Infinity", the characters "NaN" or a floating-point representation.
A floating-point representation is composed of a mantissa and an optional
exponent part. The mantissa is either a decimal point (.) followed by a
sequence of (decimal) digits, or a sequence of digits
optionally followed by a decimal point and optionally more digits. The
(optional) exponent part consists of the character "e" or "E", an optional
sign, and one or more digits.
Leading and trailing whitespace is ignored.
If the source is not a valid double literal, the onError
is called with the source as argument, and its return value is
used instead. If no onError is provided, a FormatException
is thrown instead.
The onError function is only invoked if source is a String with an
invalid format. It is not invoked if the source is invalid for some
other reason, for example by being null.
Examples of accepted strings:
"3.14"
" 3.14 \xA0"
"0."
".0"
"-1.e3"
"1234E+7"
"+.12e-9"
"-NaN"
Source
external static double parse(String source, [double onError(String source)]);