Is it possible to interpolate Javascript regex match in a string template?

user_294260 0
Viewed 1264

For example... (this fails)

const currencyMap = {
  "$": "USD",
  "€": "EUR",
};

const r = '$100'.replace(/(\$)([0-9]*)/g, `${currencyMap[$1]}$2`);
console.log(r);

Is there a way to make this sort of thing work? $1 is available when it's used in a string, but not as a key.

javascript regex
2 Answers

Unfortunately no, you'll have to use a replacer function instead:

const currencyMap = {
    "$": "USD",
    "€": "EUR",
};

const r = '$100'.replace(/(\$)(\d*)/g, (_, $1, $2) => currencyMap[$1] + $2);
console.log(r);

Also note that you can use \d instead of [0-9] instead, it makes the regex a bit nicer to read.

If you don't actually need the second group for something special, you can just echo back the match in the object:

const currencyMap = {
    "$": "USD",
    "€": "EUR",
};

const r = '$100'.replace(/[$€]/g, match => currencyMap[match]);
console.log(r);

user_95152070

Ok I've figured it out. Replace can take a function as a second arg to make the replacement string.

const currencyMap = {
    "$": "USD",
    "€": "EUR",
};

const r = '$100'.replace(/(\$)([0-9]*)/g, (full, first, second) => {
    return `${currencyMap[first]} ${second}`;
});

console.log(r);
user_2942600
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