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The Empty Statement in JavaScript

bhagatparwinder profile image Parwinder πŸ‘¨πŸ»β€πŸ’» ・1 min read

The empty statement in JavaScript is one of those fun and quirky things about JS that you should know. It might not be beneficial, but it exists, and it is entirely legal. An empty statement in JavaScript is ;. Yup, a semicolon.

An empty statement provides no statement even though JavaScript expects it. The statement has no effect and performs no action.

A typical example would be to create a for loop that has no body.

const arr = [1, 2, 3, 4, 5];

for (i = 0; i < arr.length; arr[i++] = 0) ;

console.log(arr); // [ 0, 0, 0, 0, 0 ]

It is a good idea to leave a comment if you ever plan on using an empty statement.

const arr = [1, 2, 3, 4, 5];

for (i = 0; i < arr.length; arr[i++] = 0) /* empty */ ;

console.log(arr); // [ 0, 0, 0, 0, 0 ]

Another example of using an empty statement is a chain of if-else.

const name = "Lauren";

if (name === "Parwinder")
    console.log(name);
else if (name === "Lauren")
    console.log(`Hello ${name}`); // Hello Lauren
else if (name === "Eliu"); // No action is taken if name passed is  "Eliu"
else if (name === "Robert")
    console.log(`Good to see you ${name}`);
else
    console.log("Goodbye");

Posted on by:

bhagatparwinder profile

Parwinder πŸ‘¨πŸ»β€πŸ’»

@bhagatparwinder

Happy, cheerful, confident. Web developer based out of Chicago :)

Discussion

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Actually empty statements in js can have some legitimate use cases. For example, to prevent undesired behavior in IIFE you sometime want to prefix it with empty statement, like so:

;(()=>console.log('ooof'))()
 

Ah thanks! Figured out when and what sort of undesirable behavior. If we are concatenating two JS files it could definitely cause issues. Here’s a write up with an example:

mariusschulz.com/articles/disassem...

 

Sure, and my bad, I should have specified it in the original post!

 

For those examples, rather than commenting, I'd just stick with an empty block for clarity:

for (...whatever...) { }

or

if (a) {
    doSomething();
} else if (b) {
} else if (c) {
    doSomethingElse();
}

Fewer characters and you won't have people swearing at you when they read the code.

 

Thanks for the feedback. Yup, that is why I specified if you ever plan on using an empty statement. If you don't and stick to empty blocks there is nothing to worry about.