Sometimes, we want to fix the “The left -hand and right hand side of an arithmetic operation must be of type ‘any’, ‘number’ or an enum type” error with TypeScript.

In this article, we’ll look at how to fix the “The left -hand and right hand side of an arithmetic operation must be of type ‘any’, ‘number’ or an enum type” error with TypeScript.

How to fix the “The left -hand and right hand side of an arithmetic operation must be of type ‘any’, ‘number’ or an enum type” error with TypeScript?

To fix the “The left -hand and right hand side of an arithmetic operation must be of type ‘any’, ‘number’ or an enum type” error with TypeScript, we should make sure all the operands we use with arithmetic operators are numbers.

For instance, if we’re subtracting 2 timestamps, we should make sure they’re both timestamps by calling the getTime method with the Date instances.

So we write

const d = Math.abs(new Date().getTime() - new Date(lastConnect).getTime());

to call getTime with both Date instances to return the timestamps before we subtract them.

Conclusion

To fix the “The left -hand and right hand side of an arithmetic operation must be of type ‘any’, ‘number’ or an enum type” error with TypeScript, we should make sure all the operands we use with arithmetic operators are numbers.

For instance, if we’re subtracting 2 timestamps, we should make sure they’re both timestamps by calling the getTime method with the Date instances.