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How to form a regex for a double quote that may or may not exist (Flutter)

It’s possible that I will either have

boundary=-------Embt-Boundary--1261032946D275CF

or

boundary="-------Embt-Boundary--1261032946D275CF"

and I want to just extract -------Embt-Boundary--1261032946D275CF from the String.

How should I formed the regex? I have tried boundary="?(.+)("?) but it only works for the first but for the second I’ll get the last double quote in my extracted string (eg. -------Embt-Boundary--1261032946D275CF").

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2

Answers


  1. 0

    You need:

    boundary="?([^"]+)"?

    Only one capture group used.

    JS Demo:

    const input1 = 'boundary="-------Embt-Boundary--1261032946D275CF"';
const input2 = 'boundary=-------Embt-Boundary--1261032946D275CF';
const regex = /boundary="?([^"]+)"?/;

const match1 = regex.exec(input1);
const match2 = regex.exec(input2);

console.log(match1[1]);
console.log(match2[1]);

    The regular expression matches as follows:

    Node Explanation
    boundary= ‘boundary=’
    "? ‘"’ (optional (matching the most amount possible))
    ( group and capture to 1:
    [^"]+ any character except: " (1 or more times (matching the most amount possible))
    ) end of 1
    "? ‘"’ (optional (matching the most amount possible))
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  2. 0

    I believe flutter is Dart, which uses JavaScript regex specification, yes? Use capture groups in this way:

    boundary=("?)(.*)(1)

    Group 1 will capture a quote if there is one. Group 2 will capture your desired result. Then, 1 will match the quote, if there was one, or nothing, if the quote was not present.

    regex101

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