The ternary operator is a nice way to write concise value assignments without having to write a more lengthy
// This... let value; if (test) value = 1; else valeu = 2; // can be written as this: const value = test ? 1 : 2;
However it's easy to misuse the ternary operator for things where simpler operators could often have been a better choice. So here are some alternatives for common mistakes.
Static true/false assignments:
const value = test ? true : false; // can be replaced by boolean casting: const value = !!test; // or even const value = Boolean(test); // I prefer the shorter alternative
Nullable assignment (falsy case)
const value = test ? test : null; // can be written like this const value = test || null;
Note: The code above will return null as long as
Nullable assignment (nullish case)
const value = test !== null || test !== undefined ? test : null; // can be written like this: const value = test ?? null;
By the way...
const test = a === null || a === undefined; // can be simplified as: const test = a == null;
Checking for undefined
I have seen this a few times. I promise.
const value = obj ? obj.a : undefined; // which can simply be: const value = obj && obj.a; // or in more recent implementations: const value = obj?.a;
Beware of browser coverage. If you want to use optional chaining safely, it might be a good idea to use TypeScript configured to transpile the code to ES5 with the modules configured to esnext, to use the latest ECMAScript features.
The ternary (but not actually ternary) operator
This is my favorite one, and also an honest mistake. Some people get overexcited with the simplicity of the ternary operator and might think it is just a "shorter"
let value; test ? value = 8 : null; // when they meant if (test) value = 8;
if statement is simple and clean enough for that purpose, and we know
test ? value = 8 will not work. The ternary operator needs to have an
else return value. If you don't need it, use a single-line
In a nutshell, if your ternary operator does not have a structure like the one below, you should raise an eyebrow and check if there really aren't other simpler alternatives.
const value = test ? otherValue : anotherValue;
Can you think of other examples you have seen of poor use of the ternary operator? Please let me know in the comments below.
Top comments (4)
Great list, just be careful with Optional chaining, support is only around 90%.
Also what is "The ternary operator with disability" meant to be as I don't think that is a common term and as it reads it comes across as something that could be offensive.
I understand that could just be a language issue so I thought I would ask.
I have edited out that bad attempt at humor. I'll try and keep my questionable sense of humor away from my posts. Sorry about that, and thanks for the feedback.
I am guilty of using ternary operator when I could probably use something else. Great read, I'll work on incorporating these ideas.
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