Why Is My JavaScript Regex Returning Null When Matching Points?

Why the JavaScript Regex Isn't Working

Problem:

You're encountering a null result when attempting to match a list of points in JavaScript with a regular expression.

Regex Expression:

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

Solution:

• Use a regex literal:

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

• Errors using RegExp:

  • Delimiters (/) should not be part of the expression.
  • Backslashes should be escaped if the expression is defined as a string.
  • Modifiers should be passed as a second argument to the function.

Note:

While using RegExp is an option, it's often more convenient to use regex literals.

Extracting Values:

• .match() returns an array of strings, which may not be useful.
• .exec() can be used to continuously extract numbers until the entire string is processed:

var result, points = [];
while((result = reg.exec(polygons)) !== null) {
    points.push([+result[1], +result[2]]);
}

This creates an array of arrays containing the extracted numbers. The unary plus ( ) converts the strings to numbers.

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