Arrow Function Expressions

An arrow function expression is a compact alternative to a traditional function expression, but is limited and can’t be used in all situations.

There are differences between arrow functions and traditional functions, as well as some limitations:

• Arrow functions don’t have their own bindings to this, arguments or super, and should not be used as methods.
• Arrow functions don’t have access to the new.target keyword.
• Arrow functions aren’t suitable for call, apply and bind methods, which generally rely on establishing a scope.
• Arrow functions cannot be used as constructors.
• Arrow functions cannot use yield, within its body.

Additional Resources:

Can I Use? JavaScript Arrow Functions by Wes Bos

CAVEATS

• the this context is not reset within an arrow function.

• The value of this is therefore the same as the this of the enclosing scope (the surrounding non-arrow function). If there isn’t a non-arrow function scope surrounding, the this context will be, in the browser, the global window object.

• Why does this happen? It happens because arrow functions retain the this value of the enclosing functional scope. Therefore, you will want to avoid using an arrow function in a constructor (where we need the contextual this to be the object we are building) or any method that needs to use this to behave properly.