CODEWITHSUNDEEP
javascriptregex
user2039981
user2039981

Reputation:

Javascript - RegExp - Replace last occurrence of non-number

So this is my code:

function PlusMinus() {
  str = str.replace(/([^\d\.](?!.*[^\d\.]))/, function(m, $1) {
    if ($1 == "-") return "";
    return $1 + "-";
  });
}

And it isn't working.

What I want to do, is to find the last occurrence of any character that is not a number (0-9) or a dot (.) and then if it is a "-", remove it, if it isn't replace the char with the char + "-".

Simply like a calculators -/+ button.

Examples:

"" -> "-"
"-" -> ""
"abc2-3" -> "abc23"
"a2-" -> "a2"
"s23.3" -> "s-23.3"
"4f" -> "4f-"

And yes, I've seen this: JavaScript RegExp: Can I get the last matched index or search backwards/RightToLeft? but I can't get it to work for chars in brackets

Upvotes: 0

Views: 133

Answers (2)

Niet the Dark Absol
Niet the Dark Absol

Reputation: 324810

I would say something like this:

str.replace(/(?:^|.)(?=[\d.]*$)/,function(c) {
    return c == "-" ? "" : c+"-";
});

This will find a character such that all the characters after it are either numbers or a dot. Due to the greedy nature of quantifiers and the left-to-right processing of regexes, this will be the first such character found, which will be the last non-digit, non-dot character.

However, be sure to return or otherwise do something with the result! Otherwise you're just discarding it.

Upvotes: 1

plalx
plalx

Reputation: 43728

plusMinus(''); //'-'
plusMinus('-'); //''
plusMinus('abc2-3'); //'abc23'
plusMinus('a2-'); //'a2'
plusMinus('s23.3'); //s-23.3

function plusMinus(str) {
    return str.replace(/(^|[^\d\.])(?=[\d\.]*$)/, function ($0) {
        return $0 === '-'? '' : $0 + '-';
    });
}

I am just unsure about what to do with something like 33, because now it will return -33. Is this the desired behavior?

Upvotes: 0

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