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Update "Capturing groups" files #392

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Mar 12, 2023
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Update "Capturing groups" files #392

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18 changes: 16 additions & 2 deletions 9-regular-expressions/11-regexp-groups/04-parse-expression/solution.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,8 @@ The full regular expression: `pattern:-?\d+(\.\d+)?\s*[-+*/]\s*-?\d+(\.\d+)?`.

It has 3 parts, with `pattern:\s*` between them:
1. `pattern:-?\d+(\.\d+)?` - the first number,
1. `pattern:[-+*/]` - the operator,
1. `pattern:-?\d+(\.\d+)?` - the second number.
2. `pattern:[-+*/]` - the operator,
3. `pattern:-?\d+(\.\d+)?` - the second number.

To make each of these parts a separate element of the result array, let's enclose them in parentheses: `pattern:(-?\d+(\.\d+)?)\s*([-+*/])\s*(-?\d+(\.\d+)?)`.

Expand Down Expand Up @@ -54,3 +54,17 @@ function parse(expr) {

alert( parse("-1.23 * 3.45") ); // -1.23, *, 3.45
```

As an alternative to using the non-capturing `?:`, we could name the groups, like this:

```js run
function parse(expr) {
let regexp = /(?<a>-?\d+(?:\.\d+)?)\s*(?<operator>[-+*\/])\s*(?<b>-?\d+(?:\.\d+)?)/;

let result = expr.match(regexp);

return [result.groups.a, result.groups.operator, result.groups.b];
}

alert( parse("-1.23 * 3.45") ); // -1.23, *, 3.45;
```