Why Isn't My JavaScript Regex Matching Coordinates Correctly?

Why This JavaScript Regex Isn't Working

In the provided JavaScript code, the regex var reg = new RegExp("/(s*([0-9.-] )s*,s([0-9.-] )s*)/g"); fails to match the input string var polygons="(25.774252, -80.190262),(18.466465, -66.118292),(32.321384, -64.75737),(25.774252, -80.190262)";, resulting in a null result.

Incorrect Regex Usage

The error stems from two incorrect usages of the RegExp constructor:

1. Delimiters: The forward slashes (/) should not be included as part of the regular expression string. Instead, use the /(s*([0-9.-] )s*,s([0-9.-] )s*)/g syntax to define the expression with '/' as the delimiters.
2. Escaping Backslashes: If using a regular expression string, the backslash character must be escaped with another character to ensure its literal representation, since is reserved for escape sequences in JavaScript strings.

Regex Literal

To avoid these pitfalls, it is recommended to use a regex literal, which is enclosed in forward slashes and escaped according to the regular expression syntax:

var reg = /\(\s*([0-9.-]+)\s*,\s([0-9.-]+)\s*\)/g;

Output Extraction

The polygons.match(reg) syntax used in the code returns an array of matched substrings. However, since the input string only contains a single substring that matches the pattern, the result is a single-element array:

["(25.774252, -80.190262),(18.466465, -66.118292),(32.321384, -64.75737),(25.774252, -80.190262)"]

To extract the individual lat/lon pairs as arrays, the match() method should be replaced with exec():

[total match result, lat1, lon1, lat2, lon2, ..., latn, lonn] = reg.exec(polygons);

This will result in an array containing the overall match and all captured groups, allowing for easy access to the lat/lon pairs.

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