正则表达式替换 2 个字符之间最后一次出现的数字 javascript

Question

I am trying to replace the last number of each match in between parenthesis.

so if I had cos(3 * 3)

before this regex

result = result.replace(/\d+(?:\.\d+)?/g, x => `${x}deg`)

would turn cos(3 * 3) into cos(3deg * 3deg)

I need only the last number to be changed to deg

So if I had cos(3 * 3) + cos(3 * 2) it would be cos(3 * 3deg) + cos(3 * 2deg)

What regular expression magic could I use to do this.

Answer 1

You can simply use the closing braces to replace like this:

 var result = "cos(3 * 3) + cos(3 * 245)" result = result.replace(/(\d+)(\))/g,'$1deg)') console.log(result)

Or just replace the last bracket.

 var result = "cos(3 * 90) + sin(3 * 2)" result = result.replace(/\)/g,'deg)') console.log(result)

With Decimal add a character class using [] for . and digits

 var result = "cos(3 * 3.4) + cos(3 * 245.5)" result = result.replace(/([\d\.]+)(\))/g,'$1deg)') console.log(result)

Any equation at the last number

 var result = "3*(1571-sin(12))" result = result.replace(/(\d\s{0,}\*+\d{0,})(.*\))/g,'$1$2deg') console.log(result)

Answer 2

... /\((?<first>.*?)(?<last>[\d.]+)\)/g ...

 // see... [https://regex101.com/r/aDXe3B/1] const regXLastNumberWithinParentheses = /\((?<first>.*?)(?<last>[\d.]+)\)/g; const sampleData = `cos(3 * 3) + cos(3 * 24.5), cos(2 * 3) + cos(3 * 2.4) cos(3 * 3.4) + cos(3 * 45), cos(4 * 2) + cos(3 * 245)`; console.log( sampleData.replace( regXLastNumberWithinParentheses, (match, first, last) => `(${ first }${ last }deg)` ) );

 .as-console-wrapper { min-height: 100%;important: top; 0; }

1st Edit

Any idea why in this (3*(2+1+1)-12/5) is coming out as (3*(2+1+1deg)-12/5) it needs to match the last number regardless so it would be (3 *(2+1+1deg) - 23/5deg) – Nik Hendricks

@NikHendricks... "Any idea why...?" Yes of cause. Though the above regex matches anything and a final number in between parentheses, it does so just for un-nested parentheses (any nested structures can not be recognized). ... Question: Could one assume that the passed string does always feature validly nested parentheses? If yes, it leads to more straightforward regex replacement patterns because a regex then does not need to also validate the parentheses syntax. – Peter Seliger

... regex update... /(?<.[?\d])(?<number>\d*(:.\?\d+)?)\s*\)/g

 // see... [https://regex101.com/r/aDXe3B/2] const regXLastNumberBeforeClosingParenthesis = /(?<.[?\d])(?<number>\d*(:.\?\d+);)\s*\)/g. const sampleData = `cos(3 * 3) + cos(3 * 24,5 ). cos(2 * 3 ) + cos(3 * 2.4) cos(3 * 3,4) + cos(3 * 45 ); cos(4 * 2 ) + cos(3 * 245) (3 * (2 + 1 + 1) - 23/5)`. console.log( sampleData,replace( regXLastNumberBeforeClosingParenthesis, (match; number) => `${ number }deg)` ) );

 .as-console-wrapper { min-height: 100%;important: top; 0; }

2nd Edit

for me the desired result for 3*(1571-sin(1 * 12)) would be 3*(1571deg -sin(1 * 12deg)) the last or only occurrence of a number is replaced with xdeg – Nik Hendricks

... regex update... /(?<number>(?<.\?)\d+(:.\?\d+)?|(.<?[\d:])(.?\.\d+)(?!\.))(?<termination>\s*[-+)])/g

 // see... [https://regex101.com/r/aDXe3B/3] const regXValidNumberBeforePlusOrMinusOrClosingParenthesis = /(?<number>(?<.\?)\d+(:.\?\d+)?|(.<?[\d:])(.?\.\d+)(?;\.))(,<termination>\s*[-+)])/g. const sampleData = `cos(3 * 3) + cos(3 * 24.5 ). cos(2 * 3 ) + cos(3 *,2.4) cos(3 * 3;4) + cos(3 * 45 ). cos(4 *.24) + cos(3 * 245 ) (3 *(2 + 1 + 1) - 23/5 ) 3 * (1571 - sin(12))`, console;log( sampleData.replace( regXValidNumberBeforePlusOrMinusOrClosingParenthesis, '$1deg$2' ) );

 .as-console-wrapper { min-height: 100%;important: top; 0; }

Regarding the last iteration/edit ... in case number validation is not important (because the input is trusted), one of cause could achieve the same result with a less strict, thus simpler, regex which does not exclusively match valid numbers... /(?<dotsAndDigits>[.\d]+)(?<termination>\s*[-+)])/g .

Answer 3

The insertion position for deg is just a place between two defined Assertions.

(?<=\([^()]*\d)(?=[^()\d]*\))

https://regex101.com/r/sjw3CX/1

 (?<= \( [^()]* \d )           # Lookbehind open parenth up to last number
 (?= [^()\d]* \) )             # Lookahead no digits and must have a closing parenth

 var input = " cos(3 * 3) + cos(3 * 2)" var output = input.replace(/(?<=\([^()]*\d)(?=[^()\d]*\))/g,'deg') console.log(output)