String prototype works in browser but not in node

Question

Node: 8.1.0

I have the following prototype:

String.prototype.toSlug = function () {
  return (<string>this)
    .trim()
    .toLowerCase()
    .replace(/\s+/g, '-')
    .replace(/[^\w\-]+/g, '')
    .replace(/\-\-+/g, '-')
    .replace(/^-+/, '')
    .replace(/-+$/, '')
}

When I use it, like this:

// Mongoose Database Model:
let project = new ProjectModel
project.slug = title.toSlug()

It doesn't seem to work correctly. All it did was remove the first space and add a dash as seen here:

// Original: "Bed Time Stories"
// Outputs: "BedTime-Stories"
// Expected: "bed-time-stories"

As you can see it didn't even convert the strings to lowercase.

However when I test this at jsfiddle, it creates the correct output string. What is causing this?

Is that literally how you've typed it, with `return (this)...` ? — adeneo, Aug 12 '17 at 14:32
That's Typescript, are you using that in Node as well as the Fiddle — adeneo, Aug 12 '17 at 14:34
That is a strange output, I can't really see why Typescript wouldn't be able to compile something that simple, but it seems neither `toLowerCase` or the global replacements work ? — adeneo, Aug 12 '17 at 14:38
sidenote: you can simplify this code to `return (this).toLowerCase().replace(/[\s-]+/g, '-').replace(/^-+|-+$|[^\w\-]+/g, '')` — Thomas, Aug 12 '17 at 14:53
Okay, I figured it out, it had to do with `pm2` not reloading the changes that I made for some reason... — Get Off My Lawn, Aug 12 '17 at 14:54
Please do not mutate built-in objects and/or their prototypes. — mscdex, Aug 12 '17 at 15:17

marvel308 · Answer 1 · 2017-08-12T14:59:21.663

1

interface String {
    toSlug(): string;
}

String.prototype.toSlug = function () {
  return (<string>this)
    .trim()
    .toLowerCase()
    .replace(/\s+/g, '-')
    .replace(/[^\w\-]+/g, '')
    .replace(/\-\-+/g, '-')
    .replace(/^-+/, '')
    .replace(/-+$/, '')
}

var str = "Bed Time Stories";

console.log(str.toSlug());

I found the error, The interface provides the contract for TypeScript, allowing visibility of the new method. The JavaScript implementation provides the code that will be executed when the method is called. That was missing from the code

Sources : Extending functionality in TypeScript

edited Aug 12 '17 at 14:59

answered Aug 12 '17 at 14:33

marvel308

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I am using node `8.1.0` If that makes a difference – Get Off My Lawn Aug 12 '17 at 14:40
Removing the typescript element doesn't really answer the question. – Andy Aug 12 '17 at 14:41
I believe I found the error, please see updated answer – marvel308 Aug 12 '17 at 14:56
I had that in my code, I just didn't post it. But the answer was that my `pm2` was not loading changes even though it was watching for changes. Killing the `pm2` process and starting a new one fixes the issue. – Get Off My Lawn Aug 12 '17 at 14:59

String prototype works in browser but not in node

1 Answers1