How can I use async/await at the top level?

How to Use async/await at the Top Level in JavaScript

Welcome to my tech blog, where I break down complex coding problems into digestible pieces! 🚀 Today, we're going to tackle the common issue of using async/await at the top level in JavaScript.

One of my readers sent in a question, and it goes like this:

"I have been experimenting with async/await, and I can't seem to figure out why my code doesn't work as expected. Could you shed some light on the matter?"

Of course, my friend! Let's dive right in and look at the code snippet provided:

async function main() {  
    var value = await Promise.resolve('Hey there');
    console.log('inside: ' + value);
    return value;
}

var text = main();  
console.log('outside: ' + text);

When you run this code, you'll notice that the console output is not what you expected. It looks like this:

> outside: [object Promise]
> inside: Hey there

Now, let's break it down step by step.

Understanding the Issue

The issue here is that main() is an asynchronous function. When you call it, it returns a promise. In this case, the value of text is a promise object, not the resolved value of the promise.

So, the console.log('outside: ' + text) statement is executed immediately after calling main(), which is why you see [object Promise] instead of the expected value of 'Hey there'.

The Solution: Using an Immediately Invoked Function Expression (IIFE)

To access the resolved value of the promise without using .then(), you can wrap your code inside an immediately invoked function expression (IIFE). Here's how you can modify your code:

(async () => {
    var value = await Promise.resolve('Hey there');
    console.log('inside: ' + value);
    return value;
})();

By wrapping the async/await code inside the IIFE, you ensure that it is immediately executed. This way, you can access the resolved value directly, without assigning it to a variable.

Putting It All Together

Let's go back to our original code snippet and modify it using an IIFE:

(async () => {
    var value = await Promise.resolve('Hey there');
    console.log('inside: ' + value);
    return value;
})();

Now, when you run the code, you'll get the desired output:

> inside: Hey there

Conclusion

Congratulations on making it through! 🎉 We've successfully tackled the issue of using async/await at the top level in JavaScript. Remember to use an IIFE to immediately invoke your asynchronous code and access the resolved value without using .then().

I hope you found this guide helpful! If you have any more questions or need further clarification, feel free to leave a comment below. Happy coding! 💻