Implicit Conversion

Arithmetic Operations

Addition

string + any

String concatenation, non-string types are converted to string

number + primitive types except string

Non-number types are converted to number

number + non-primitive

Both sides are converted to string

Subtraction, Multiplication, Division

Non-number types on either side are converted to number

Logical Operations

As standalone conditions

null, undefined, '', NaN, ±0, 0n, false

falsy ¹

Others

Truthy

Non-strict comparison ==

NaN == any

false - including NaN == NaN

boolean == other

boolean converted to number

string == number

string converted to number

null == any

true when any is null or undefined

false otherwise

undefined == any

true when any is null or undefined

false otherwise

Primitive == Non-primitive

Non-primitive converted to primitive before comparison ²

最后更新时间: 2025年09月14日