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Why not to use `&&` in JSX ?

Mardi Himal
Mardi Basecamp by Sanjay Hona

It’s generally a good practice to write fewer lines of code for a feature in a project and this is somehow part of the clean code momentum. Because of this, we tend to use shorthand operators like &&, || for checking certain conditions in javascript. For example

HelloWorld.jsx

const HelloWorld = ({ name }) => {
  return name && <Text>Hello World ${name}</Text>;
};

Main.jsx

const name = 'roshan';

return <HelloWorld name={name} />;

It looks like a perfect block of code, doesn’t it ? It actually is. It takes less lines of code and looks clean but what happens if something goes wrong and name prop that we are sending to HelloWorld component is empty ("") ?

Before answering the question, let me just mention a very basic idea on how comparison works in javascript.

'' && true; // ""
true && ''; // ""
false && true; // false

As you can see here, && is a boolean operator which returns the value of a falsy one when both operands aren’t truthy.

Let’s revisit the above code with slight modification i.e name is now empty instead of proper value.

const HelloWorld = ({ name }) => {
  return name && <Text>Hello World ${name}</Text>;
};

const name = '';

return <HelloWorld name={name} />;

Now, return part of the HelloWorld component will now look like:

return '' && <Text>Hello World ${name}</Text>;

and according the basic comparison principle that I mentioned above, the output would be the falsy part of the comparison which is "". This is not what we wanted to return, right ? "" is not even a valid component.\

In react native, this will actually result in hard crash which looks like this:



Solution?

Personally, I almost always try to avoid using && operator while comparing things in JSX. I prefer using ternary operators ? : instead. Unlike && operator, ternary operators do not increase the cognitive complexity of the code as the only purpose of ternary operators is to compare two values. I find it more readable and concise.

But if you insist in using && , then I would recommend you to wrap the variable (name in this case) with Boolean or use double negation !! to cast it to boolean value.

Boolean(name) && <Text>Hello World \${name}</Text>;

OR

!!name && <Text>Hello World \${name}</Text>;

I hope you find this article helpful. See you in the next one.
Keep learning!