Decrypting Arrow Functions: new What happens with an arrow function?

Arrow Functions (Arrow Functions) is a powerful feature introduced in ES6 that simplifies the way functions are written and improves scope binding. However, arrow functions have some important differences from traditional function expressions, one of which is that they are not suitable for use as constructors. newIn this article, we will delve deeper into this issue and understand what happens when using arrow functions .

Introduction to arrow functions

First, let’s review the basic syntax of arrow functions:

// 代码
const add = (a, b) => a + b;

Arrow functions are often used to create anonymous functions and automatically bind this to the external context. This makes arrow functions very useful when working with callback functions and simplifying code.

Why shouldn't you use newan arrow function?

In JavaScript, we can use newoperators to create instances of objects. Typically, we use constructors to achieve this, for example:

// 代码
function Person(name) {
  this.name = name;
}

const person = new Person('Alice');

However, arrow functions do not have their own thisbindings; they capture the context in which they are created this. That's why they cannot be used as constructors like normal functions.

Attempting to use newan arrow function results in an error:

// 代码
const Example = () => {
  this.value = 42;
};

const instance = new Example(); // TypeError: Example is not a constructor

In the example above, we try to newcreate an Exampleinstance of a using the keyword, but since Exampleit's an arrow function, it doesn't have constructor capabilities, so it throws TypeError.

code example

To understand this better, we can look at a practical example. Let's say we have an arrow function to create a simple object:

// 代码
const createPerson = (name) => ({
  name,
});

const person = createPerson('Bob');
console.log(person); // { name: 'Bob' }

The createPerson function above returns an object literal that contains a name attribute. This function works well with arrow functions because it does not require this binding.

Summarize

In JavaScript, arrow functions are very powerful and useful, but they are not suitable for use as constructors. Therefore, try to avoid using new to instantiate arrow functions to avoid causing errors. If you need to create instantiable objects, you should still use traditional constructors or classes. Arrow functions are designed to simplify the writing of function expressions, not for object instantiation.