Magic Comments

Magic comments log the value of an expression to the output pane without modifying what your code does. Add //? after a statement to print its value:

[1, 2, 3].map(n => n * 2) //?

The block form /*?*/ can be used inline, mid-expression:

a.b().c() /*?*/ .d()

It also works before the opening brace of a block — useful for inspecting the condition of an if or each iteration of a loop:

if (user.role === 'admin') /*?*/ {
  // ...
}

for (const item of items) /*?*/ {
  // ...
}

Anything written after the marker is evaluated as JavaScript, with $ referring to the value of the expression. Use this to log a derived value instead of the whole thing:

users //? $.map(u => u.name)

items.filter(i => i.active) //? $.length