Accessing a variable using the `window` object in JavaScript might make your code run a tad slower. Let's dive into why that happens and what you can do to optimize your code for better performance.
Let's first understand the `window` object in JavaScript. The `window` object represents an open window in a browser and stores properties that relate to the document, history, location, and more. When you access a variable using the `window` object, JavaScript needs to traverse up the scope chain to find the variable, which introduces some performance overhead.
When JavaScript looks for a variable, it starts from the innermost scope (where the variable is used) and then moves up through the scope chain until it finds the variable. If the variable isn't found in the local scope, it continues up to the global scope, which includes the `window` object.
Now, why is accessing a variable through the `window` object slower? Well, when you access a variable that is directly available in the local scope, JavaScript can quickly find and retrieve its value. However, when you use the `window` object to access a variable, JavaScript has to perform additional lookups up the scope chain, which adds overhead to the process.
To improve performance when accessing variables, consider storing frequently accessed variables in a local scope where possible. By avoiding unnecessary traversals up the scope chain, you can reduce the time it takes for JavaScript to locate and retrieve the variable.
Another way to optimize your code is to use object destructuring to extract variables from the `window` object if you need multiple properties. Instead of accessing each property through the `window` object individually, you can destructure them into local variables for faster access.
// Instead of:
const width = window.innerWidth;
const height = window.innerHeight;
// Use destructuring:
const { innerWidth: width, innerHeight: height } = window;By destructuring properties from the `window` object, you eliminate the need for repeated lookups, which can improve performance, especially when working with multiple properties.
In conclusion, while accessing variables using the `window` object may introduce some performance overhead due to traversing the scope chain, you can optimize your code by storing frequently accessed variables in local scopes and using object destructuring for multiple properties. By being mindful of how you access variables, you can enhance the performance of your JavaScript code.