How to add symbol in regular expression by condition? - regex

Question

I need to add 0 if a founded number is less than 10 in the regular expression:
My expressions:
searching string:
"createdAt":\s+\[\s+([0-9]+),\s+([0-9]+),\s+([0-9]+),\s+([0-9]+),\s+([0-9]+),\s+([0-9]+)\s+]
replacing:
"createdAt": "($1)-($2)-($3)T($4):($5):($6)"
Result:
Input data:
"createdAt": [
2022,
4,
15,
13,
43,
7
]
Expected output data:
"createdAt":"2022-04-15T13:43:07"
Actual output data (4 except 04 and 7 except 07):
"createdAt":"2022-4-15T13:43:7"
--
So, how to add conditions in this case?

Answer 1

If you're ok with manipulating the array:
const json = {
"createdAt": [
2022,
4,
15,
13,
43,
7
]
}
const formattedJson = json.createdAt.map((n) => n.toString().padStart(2, 0))
console.log(formattedJson);
Or using regex on the date string:
const date = "2022-4-15T13:43:7"
const formattedDate = date.replace(/\b(\d)\b/g, '0$1')
console.log(formattedDate);
Breakdown of /\b(\d)\b/g
\b - Word boundary. In this case we're wrapping a boundary around any single digit.
\d - Any digit 0-9
() - Capturing group. This allows us to reference anything between the parentheses at a later point.
This is the replacement '0$1'. The $1 is how we reference the capturing group. If we had multiple capturing groups, we'd reference the second one with $2, the third with $3, etc..
In this case we're just saying - look for any single digit and replace it with a 0 and the digit itself.