Regular expression to validate sum of numerics - regex

Question

I want to validate the user input,
it should accept,
1+2
1.2+56+3.5
it should not accept any alphabets, special characters other than . and +
and mainly it should not accept ++ and ..
please help me with regular expression.

Answer 1

This should work:
var regex = /^[0-9]+(\.[0-9]+)?(\+[0-9]+(\.[0-9]+)?)*$/;
"1+2".match(regex); // not null
"1.2+56+3.5".match(regex); // not null
"1++2".match(regex); // null
"1..2".match(regex); // null
online: http://regex101.com/r/zJ6tP7/1

Answer 2

Something like this should suffice
^([+]?\d+(\.\d+)?)*$
http://regex101.com/r/qE2kW1/2
Source: Validate mathematical expressions using regular expression?

Answer 3

Note that I'm assuming it should not accept .+ or +. as well. I'm not assuming that you require checking for multiple decimals prior to an addition, meaning this will accept 3.4.5 I'm also assuming you want it to start and end with numbers, so .5 and 4+ will fail.
(\d*[\.\+])*(\d)*
This takes any amount of number values, followed by a . or a +, any number of times, followed by any other number value.
To avoid things like 3.4.5 you'll likely need to use some sort of lookaround.
EDIT: Forgot to format regular expression.