How devtools map minified JS code back to your TypeScript source code | Hacker News Reader

How devtools map minified JS code back to your TypeScript source code

polarsignals.com

107 pointsmanojvivek16 comments

Tangentially related, but last year I've made a tool to recover original sources from web apps which expose source maps (with the sourcesContent value present), including enumerating all lazily loaded chunks:

https://github.com/zb3/getfrontend

Recent related post where Apple seemingly forgot to disable source maps for the App Store

Apple's App Store Full Front End Source Code

https://news.ycombinator.com/item?id=45804664

edit: formatting

I love it when things are displayed so nicely on mobile. This could've been a pain to read and get through but it was actually quite pleasant.

> Notice how the decoded values give relative positions, each value represents the difference from the previous position, not absolute coordinates. This is crucial: instead of encoding large column numbers like 27698 in minified files, source maps only store small deltas like +7 or +15, making the encoded strings much more compact.

Wouldn't "offset" be a more apt term?

To me, “offset” sounds more like the distance from the start, whereas here the values are relative to the previous segment. Not a native english speaker, so I could be wrong.

Offset is difference from a starting point or a previous position

“Offset” is not enough on its own. Offset from what? Start of file? Absolute offset. Previous offset? Relative offset.

2nd order offset. The offset from the <offset from the start of the file>

perhaps the delta between offsets

We’re gonna need the delta of deltas

It sounds equally apt to my ear. I've used both words for this concept in the past.

Delta Encoding is the common term

Agreed... Delta Encoding, or even Delta Offset would work together.

In this case I feel it's like six of one and a half-dozen of the other.

Delta definition 4: (mathematics, physics, engineering) The symbol Δ; A change in a quantity, likely from "d" for "difference"

Offset definition 7: The distance by which one thing is out of alignment with another.

Got these from Wiktionary:

* https://en.wiktionary.org/wiki/delta

* https://en.wiktionary.org/wiki/offset

Delta and offset mean the same thing — the difference between two amounts.

Delta is perhaps slightly more obscure outside of a math setting. Perhaps.

I feel like choosing the synonym that happens to be one letter shorter when the operation is literally intended to track things in a way that's more conscise is about as "apt" as it could be!

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