A proportional sans-serif font with extra left padding in capital case letters. And wider a space glyph.

Here’s a side-by-side with one of the most readable monospace typeface.

• Remove the padding around === so it can be used for a solid long line
• Make " longer, so it's easier to read e.g. '"foo"', also add more horizontal spacing.
• Larger return ligature
• Ligature for >>= <<= += -= *=
• Ligature for // closer together
• Ligature for ...
• Ligature for ../ (for directories ../../)
• Ligature for ()
• Ligature for export (not so fancy as return but more visible)
• Ligature for throw (not so fancy as return but more visible)
• Ligature for then in the bold font (but to make lighter and thinner)
• Ligature for this (smaller)
• Ligature for async and await (maybe italic)
• More space around / for imports (bold and regular)
• More space around . (but not much more)
• More space around ( and )
• More space before M

• Try another font, because this one is too large (byte size). I guess it’s because I naively made the bold font by offsetting the normal one.
• Alternatively, in monospaced fonts, condense capital case letters.

Modified with FontForge.