Check for an empty value in JavaScript

When I started learning JS, one of the most powerful tools I discovered, was the ability to check if a variable is empty.

My definition of emptiness was hardly a scientific one as I didn’t mean to check if it was defined or not. I wanted to take full advantage of JavaScript as a dynamically typed language.

So, I had a function that should do something useful when it’s supplied with a valid (non-empty) argument.

const doSomethingUseful = (param) => {
  if (!param) {
    console.log('param is missing or empty');
    return false;
  }
  console.log(param);
  // ... the rest of the logic follows
}

In this example if you call the function doSomethingUseful with a falsy value, it will print the string param is missing or empty and return false.

Here’s how it works:

doSomethingUseful();
doSomethingUseful(false);
doSomethingUseful(0);
doSomethingUseful('');
doSomethingUseful(null);
doSomethingUseful(undefined);

In all these cases, you’ll see the string param is missing or empty logged to the console.