The reason is that the core syntax highlighter (https://atom.io/packages/language-javascript) is heavily unoptimized, and tries precomputing data for the whole line without considering that only the first 0.5k characters will probably be seen.
It is too bad, as this was already fixed globally in existing web text editors such as CodeMirror. Given that it is used in Chrome and Firefox' DevTools, and that JS minification happens on the Web, it had to.
However, as I understand it, the issue is not so much with raw size (although it does not help) as it is with long lines.
For instance, the following 161K file freezes completely Atom, to the point that you just have to close it: https://github.com/espadrine/aulx/blob/master/html/tokenizer...
The reason is that the core syntax highlighter (https://atom.io/packages/language-javascript) is heavily unoptimized, and tries precomputing data for the whole line without considering that only the first 0.5k characters will probably be seen.
It is too bad, as this was already fixed globally in existing web text editors such as CodeMirror. Given that it is used in Chrome and Firefox' DevTools, and that JS minification happens on the Web, it had to.