It's because Scratch's String.prototype.trim polyfill is broken: run '\t'.trim() on scratch.mit.edu then any other website. This in turn affects isWhiteSpace(). The unminified polyfill script that scratch-www is based on has a \t sequence, which a minifer converted to a literal tab character, which a text editor then converted to four spaces.
https://scratch.mit.edu/projects/788261699/
It's because Scratch's String.prototype.trim polyfill is broken: run
'\t'.trim()on scratch.mit.edu then any other website. This in turn affects isWhiteSpace(). The unminified polyfill script that scratch-www is based on has a\tsequence, which a minifer converted to a literal tab character, which a text editor then converted to four spaces.