"1.233e+23",
"1.233"

##</code><code>##

"1.2e+233"

##</code><code>##

 /^([+-]?)(?=\d|\.\d)\d*(\.\d)?([Ee]([+-]?\d+))?$/

##</code><code>##

/^([+-]?)(?=\d|\.\d+)\d*(\.\d+)?([Ee]([+-]?\d+))?$/