CODEWITHSUNDEEP
javascriptregex
Praveen Kumar
Praveen Kumar

Reputation: 103

validate page ranges for printing regular expression

I need Regular Expression that validates the page ranges. (Eg. Print custom pages)

Currently, I have tried this expression

/^(?!([ \d]*-){2})\d+(?: *[-,] *\d+)*$/

It should accept values like 

 1, 3, 6-9
 1-5, 5
 6, 9

It should not accept values like

 ,5
 5-,9
 9-5,
 2,6-
 10-1

Upvotes: 3

Views: 1141

Answers (1)

aloisdg
aloisdg

Reputation: 23541

At that point I wont bother with a regex hard to read by a neophyte. A regex-free, but verbose, solution with pure js:

  • We split by comma
  • We trim all trailing whitespaces
  • We check if each part are valid
  • We return false when a falsy range is found

Demo:

const isNumeric = input => !isNaN(input) // you may also check if the value is a nonzero positive integer
const isOrdered = (start, end) => parseInt(start) < parseInt(end)
const isRangeValid = range => range.length == 2 && range.every(isNumeric) && isOrdered(range[0], range[1])
const isSingleValid = single => single.length == 1 && isNumeric(single[0])

function f(input) {
    const inputs = input.split(',').map(x => x.trim());

    for (const x of inputs) {
        if (!x) return false;
        const pages = x.split('-');
        if (!isSingleValid(pages) && !isRangeValid(pages))
            return false;
    }

    return true;
}

console.log(f("1, 3, 6-9"))
console.log(f("1-5, 5"))
console.log(f("6, 9"))

console.log(f(",5"))
console.log(f("5-,9"))
console.log(f("9-5,"))
console.log(f("2,6-"))
console.log(f("10-1"))
console.log(f("56-0"))

Try it online!

Upvotes: 5

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