Positive lookbehind and Safari workaround

Question

so i have a file of lines like so....

valueA +920.32 % valueA +479.89%
valueB +886.82 % valueB +424.59%
--- insert more similar lines ---

And I was using the following Regex to get only the two percents and store them in an array

myObject.valueA = text.match(/(?<=valueA)(?:.+?(?=%))/g);

resulting in which is what I desire

valueA: Array [ " +920.32 ", " +479.89" ]

I was very happy with that, and keep moving forward with my little project until I was trying to test it with my friend on an iPhone, and nothing happened. Which I have found out is due to safari not supporting positive look behinds so I have been looking for something to produced a similar result.

With a positive look ahead I got close but it included 'valueA ' in the result which i really don't want to have to remove with an extra line of code.

(?=valueA)(?:.+?(?=%))

Result

valueA: Array [ "valueA +920.32 ", "valueA +479.89" ]

I'm sure there's a simple way to do this, but I've been messing around on RegExr and had no luck. Thank you ahead of time.

That still includes 'valueA' itself which is the same issue i have with a positive lookahead — Muamer Bektić, Apr 28 '21 at 18:32
ah sorry! I see that now, but it doesn't seem to grab both +920.32 and +479.89 which i am trying to accomplish. Unless I am doing something wrong. — Muamer Bektić, Apr 28 '21 at 18:40
Wrong dupe. Question is specific to Safari issue of lookbehind not supported instead of just finding test between 2 strings. — anubhava, Apr 28 '21 at 20:03

score 2 · Accepted Answer · answered Apr 28 '21 at 18:55

2

You can use this workaround using capture groups in matchAll method:

const s = `valueA +920.32 % valueA +479.89%
valueB +886.82 % valueB +424.59%`

var arr = [...s.matchAll(/\bvalueA\s+([^\s%]+)/g)]

arr.forEach(el => console.log( el[1] ))

answered Apr 28 '21 at 18:55

anubhava

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almost perfect went from this... `myObject.valueA = text.match(/(?=valueA)(?:.+?(?=%))/g);` to this `myObject.valueA = [...text.matchAll(/\valueA\s+([^\s%]+)/g)]; myObject.valueA.forEach((el, i) => myObject.valueA[i]= el[1]);` Not one line anymore but better than my solution – Muamer Bektić Apr 28 '21 at 19:45

score 1 · Answer 2 · answered Apr 28 '21 at 18:31

1

If thats really what the data looks like why not just capture +, ., and digits? ([\+\d\.]+)

const text = `valueA +920.32 % valueA +479.89%`;

console.log(text.match(/([\+\d\.]+)/g))

answered Apr 28 '21 at 18:31

dave

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because the data will have several lines with 32 possible values. not every value will be included and they may not always be in the right order, so I can't just assume that the first two numbers go to valueA – Muamer Bektić Apr 28 '21 at 18:34

Positive lookbehind and Safari workaround

2 Answers2