🔰arrow function

(ES6) a new form of function expression.

JS ⟩ value ⟩ function ⟩ arrow function

⭐️ ES6 (2015)：a new form of function expression.

a => expression       // one statement: {...} optional
(a, b) => expression  // multiple params: (...) required
a => { statement1; statement2; } // multiple statements: {...} required

when the { ... } are omitted, a return value is sent out without using return.

doesn’t have own bindings to this, arguments or super.

⭐️ arrow function as method❗️ (❗️use with caution❗️)

normally, you don't use arrow functions as methods, but if you have：

an object A that has a method returning a new object B,
object B has its own methods,
you don't want this in these methods to refer to B but refer to A instead,

then using arrow functions as methods is an option.

👉 see example： Sequence

aren't suitable for call, apply and bind methods, which generally rely on establishing a scope.
don't have access to new.target keyword.
can’t be used as constructors. (can’t be called with new)
can’t use yield, within its body.

deplicate parameters Early Error rule (🚧) is always applied to arrow function definition even if 'strict mode' (🚧) is not defined explicitly.

👉 see arrow function returning object literal needs (...)❗️

const user = () => { name: 'Gandalf', age: 2019 };
// ❌ wrong syntax       ↳ ⛔️ SyntaxError: Unexpected token ':'

const user = () => ({ name: 'Gandalf', age: 2019 });
// ✅ wrap object literal in parentheses

can be used as a bound method in class field.
can be used in IIFE.
register handler with arrow functions will lose this context.
async arrow function

PreviousIIFE Nextarrow function as method❗️

Last updated 2 years ago