Parsing array syntax using regex in javascript

Question

I found the answer for this here but it's in php.

I would like to match an array like [123, "hehe", "lala"] but only if the array syntax is correct.

I made this regex /\["?.+"?(?:,"?.+"?)*\]/.

The problem is that if the input is [123, "hehe, "lala"], the regex match, but the syntax is incorrect.

How can I make it only match if the array syntax is correct?

My problem is making the second " required when the first "is matched.

Edit: I'm only trying to do it only with strings and numbers inside the array.

What about arrays inside of arrays? Do you need to handle those? Or just arrays of strings and numbers? — Ray Toal, Feb 20 '19 at 17:19
Your `.+` do not restrict much, only line breaks. Also, you are missing anchors, `^` and `$`, on both sides. Note that you need to make sure you support escape sequences, too. It is hardly a job for a regex in the end, though possible. — Wiktor Stribiżew, Feb 20 '19 at 17:19
What about escaped strings eg.. `["John said \"Hello\".", 4,5,6]` — Keith, Feb 20 '19 at 17:22
I haven't think about escaped strings, but it's possible and a good thing to consider — Vencovsky, Feb 20 '19 at 17:27
@str It's what I was just about to suggest.. :) `try { JSON.parse('["one", 1,2]'); console.log("valid"); } catch(e) { console.log("invalid"); }` — Keith, Feb 20 '19 at 17:27
But I want to match an array syntax in a string, my input isn't a stringfied object — Vencovsky, Feb 20 '19 at 17:28
You [won't like it](https://regex101.com/r/NZJzlX/1): `/^\[\s*(?:\d+|"[^"\\]*(?:\\[^][^"\\]*)*"|'[^'\\]*(?:\\[^][^'\\]*)*')(?:\s*,\s*(?:\d+|"[^"\\]*(?:\\[^][^"\\]*)*"|'[^'\\]*(?:\\[^][^'\\]*)*'))*\s*]$/` — Wiktor Stribiżew, Feb 20 '19 at 18:07

score 2 · Accepted Answer · answered Feb 20 '19 at 17:43

You can try this regex: /\[((\d+|"([^"]|\\")*?")\s*,?\s*)*(?<!,)\]/

Each item should either

"([^"]|\\")*?": start and end with ", containing anything but ". If " is contained it should be escaped (\").

\d+: a number

After each item should be

\s*,?\s*: a comma with any number of spaces before or after.

And before the closing bracket should not be a comma: (?<!,)

Demo: https://regex101.com/r/jRAQUc/1

Alexis Wilke · Answer 2 · 2019-02-21T03:43:27.327

You must have two (or more) separate expressions (using the | operator) in order to do that.

So it would be something like this:

/\[\s*("[^"]*"|[0-9]+)(\s*,\s*("[^"]*"|[0-9]+))*\s*\]/

(You may also want to use ^ at the start and $ at the end to make sure nothing else appears before/after the array: /^...snip...$/ to match the string from start to finish.)

If you need floating point numbers with exponents, add a period and the 'e' character: [0-9.eE]+ (which is why I did not use \d+ because only digits are allowed in that case.) To make sure a number is valid, it's much more complicated, obviously (sign, exponent with/without sign, digits only before or after the decimal point...)

You could also support single quoted strings. That too is a separate expression: '[^']*'.

You may want to allow spaces before and after the brackets too (start: /^\s*\[... and end: ...\]\s*$/).

Finally, if you want to really support JavaScript strings you would need to add support for the backslash. Something like this: ("([^"]|\\.)*").

Note

Your .+ expression would match " and , too and without the ^ and $ an array as follow matches your expression just fine:

This Array ["test", 123, true, "this"] Here

Parsing array syntax using regex in javascript

2 Answers2