Nearly every category except for one from "any" (all varieties but one)

In Typescript, is it feasible to specify a type for a variable where the values can be any value except for one (or any other number of values)? For instance:

let variable: NOT<any, 'number'>

This variable can hold any type of value except for 'number'.

Answer №1

When working with Typescript, you can make use of the Exclude helper function that utilizes Conditional Types introduced in version 2.8. The purpose of Exclude<T, U> is to essentially evaluate whether a particular type T extends another type U. If this condition is met, it will result in the type never; otherwise, it will retain the original type T.

function checkType<T>(value: Exclude<T, number>): void {
    console.log('This is not a number!');
}

checkType('example');
checkType([1]);
checkType(1); // This call will fail

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