Knowing how to solve the error “The left-hand side of an arithmetic operation must be type ‘any’, ‘number’, ‘bigint’ or an enum type” will help you to know more about how to work with the arithmetic operator. So how to do it? Let’s go into detail now.
The reason for the error “The left-hand side of an arithmetic operation must be type ‘any’, ‘number’, ‘bigint’ or an enum type”
This error happens when you use an arithmetic operation with a value that does not type ‘number’, ‘enum’, ‘bigint’… etc.
Example of how this error happens:
const dateType = new Date();
const anObj = {
name: "Garett Crooks",
age: 23,
eye: "colorBlue",
hair: "HairWavy, Black",
};
const err = anObj - dateType;Error:
The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.
The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.Here I get the error because on the left-hand side of the arithmetic operation, I am using object type, and the right-hand side is date type, so it is not allowed in Typescript.
Or with string type:
Example:
const theError = '10' - '9'The error:
The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.
The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.Here I also get the error when using arithmetic operations with string type.
You can read more about basic type here.
Solutions for this error
Convert to the correct type
The obvious solution here is to convert all wrong types that get the error to the correct type, which is the number type.
With date type, you can convert the value to number type by converting time to milliseconds or only using a particular date, month, or year.
Example:
const dateNow= new Date()
const anotherDate = new Date('2022-1-5');
// GetTime method will convert time to milisecond
const milisecond = dateNow.getTime() - anotherDate.getTime()
console.log(milisecond)
// GetYear method will return year
const year = dateNow.getFullYear() - anotherDate.getFullYear()
console.log(year)
// GetMonth method will return month
const month = dateNow.getMonth() - anotherDate.getMonth()
console.log(month)
// GetDate method will return date
const date = dateNow.getDate() - anotherDate.getDate()
console.log(date)Output:
[LOG]: 25519852635
[LOG]: 0
[LOG]: 9
[LOG]: 22 Use Number constructor
You can use the Number constructor to convert some specific string to the number type.
Example:
const value = Number('10') - Number('9')
console.log(value)Output:
[LOG]: 1Summary
In this article, I showed you how to fix the error “The left-hand side of an arithmetic operation must be type ‘any’, ‘number’, ‘bigint’ or an enum type”. When working with the arithmetic operation, you should convert your wrong type to some correct type, like a number.
Maybe you are interested:
- Index signature for type ‘#’ is missing in type ‘##’ in TypeScript
- Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type
- Yield expression implicitly results in an ‘any’ type in TypeScript
Hello, guys! I hope that my knowledge in HTML, CSS, JavaScript, TypeScript, NodeJS, ReactJS, MongoDB, Python, MySQL, and npm computer languages may be of use to you. I’m Brent Johnson, a software developer.
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