IT DEPENDS

Reading the code symbols

The code in this book is set in a font that joins some characters into a single shape. => prints as an arrow and === as one long bar. Nothing changes at the keyboard: you still type the separate characters in the middle column. This key lists every combination that joins somewhere in the book.

Comparison and logic

Printed glyphCharacters to typeMeaning
======Strict equality.
!==!==Strict inequality.
!=!=Loose inequality. The book uses it only as != null, which rules out both null and undefined.
<=<=Less than or equal to, greater than or equal to.
>=>=
&&&&Logical AND: the right side runs only when the left is truthy.
||||Logical OR: the right side runs only when the left is falsy.
????Nullish coalescing: the right side is used only when the left is null or undefined.
?.?.Optional chaining: the access stops, giving undefined, when the left is null or undefined.

Functions and types

Printed glyphCharacters to typeMeaning
=>=>Separates an arrow function’s parameters from its body, or a function type’s parameters from its return type.
?:?:An optional property or parameter. ? makes it optional, and : starts its type.
......Spread or rest. In comments and strings, it just means text left out.
++++Add one, subtract one. In commands, -- starts a long option such as --noEmit.
----

Comments

Printed glyphCharacters to typeMeaning
////Starts a comment that runs to the end of the line.
/*/*Start and end a block comment.
*/*/
/**/**Starts a documentation comment.

Punctuation that only looks joined

Printed glyphCharacters to typeMeaning
>>>>Two or three type-argument lists closing together.
>>>>>>
>]>]Closing brackets next to each other.
}}}}
____Two underscores in a name.
....The parent folder in a file path.
------The old-file and new-file headers in a diff.
++++++