Type Conversions

Type conversion means changing one kind of value into another.

Sometimes you do it on purpose. Sometimes JavaScript does it quietly.

Think of translating stickers from one language to another.

To string

Use String() or toString().

To number

Use Number(), parseInt(), or parseFloat().

Bad text becomes NaN.

To boolean

Use Boolean().

Remember falsy values become false.

Quiet conversion

Operators can convert types without asking.

Plus with a string often makes more string.

Unary plus

A lonely + in front can force a number.

Be clear on purpose

Convert yourself when you know what you want.

Clear code beats surprise magic.

Tip: If math looks wrong, print typeof on each piece. Quiet string conversion is a common culprit.