Regular experession to match math block - regex

Question

Hi I need to match math block in string. The math block starts with $$ and ends with $$. There can be any number of math blocks.
for example input can look like:
abcd... asdfasdf
$$
math expression
$$
<another set of random words>
$$
expression
$$
...
What is the right regex to match only the math expressions?
Thanks.

Answer 1

you could try /\$\$((?:\$[^\$]|[^\$])+)\$\$/g and that will match anything between $$ and $$ including single $.
Example:
http://regexr.com/3gu75
let text = document.body.innerHTML;
let regex = /\$\$((?:\$[^\$]|[^\$])+)\$\$/g,
match;
while( (match = regex.exec(text)) != null) {
console.log(match[1].trim());
}
abcd... asdfasdf
$$
math expression
$$
another set of random words
$$
expression
$$
$$
expression with a $ symbol
$$

Answer 2

I don't know what is typescript, but i looked it up it's like javascript. Why don't you use new RegExp()?
like new RegExp(/^\$\$.+\$\$$/g).exec(your str)
Char .+ will detect any character and so on until it find $ at the end. You can change this into your specific condition to match

Answer 3

Assuming that every odd-numbered $$ starts a math mode block, and every even-numbered one ends the previous block, you could just split the string on $$ and take the odd elements of the array:
> str=`abcd... asdfasdf
$$
math expression
$$
<another set of random words>
$$
expression
$$`
> str.split("$$").filter((s, index) => index % 2 === 1)
Array [ " math expression ", " expression " ]
The array still contains the leading and trailing spaces - you can use String.trim to get rid of them.