Tips for efficiently saving a group of regular expression values in a JSON document and accessing them in JavaScript

In my Javascript file, I have an array variable that is intended to be used with the Purgecss whitelistPatterns option, specifically within the gulp-purgecss plugin:

var purgeWLP = [
    /^carousel-item.*/,    
    /collapsing/,           
    /show/,                
];

I want to keep this array and other project variables in an external .json file for easy access across different files. Here's what I've tried:

{
    "wlp": [
        "/^carousel-item.*/",
        "/collapsing/",
        "/show/"
    ]
}

However, I am facing errors and not achieving the desired outcome, which is to replicate the results of the purgeWLP variable inside the javascript file.

How can I correctly store an array of regex values in a .json file and retrieve it in Javascript?

javascriptarraysjsongulppurge

Answer №1

To keep them as strings without the slashes, store them that way and then convert them into RegExp objects after parsing the JSON string:

const json = `{
    "wlp": [
        "^carousel-item.*",
        "collapsing",
        "show"
    ]
}`

const wlp = JSON.parse(json).wlp // or const wlp = require('./project.json').wlp on nodejs
  .map(str => new RegExp(str))

console.log(wlp)

For saving them, you can utilize JSON.stringify() and map each RegExp object to its source string (refer to this comment by Emanuel Vintilă):

var purgeWLP = [
    /^carousel-item.*/,    
    /collapsing/,           
    /show/,                
];

var result = JSON.stringify(purgeWLP.map(re => re.source));

console.log(result);

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