Sometimes, we want to fix the ‘Cannot invoke an expression whose type lacks a call signature’ error in TypeScript.
In this article, we’ll look at how to fix the ‘Cannot invoke an expression whose type lacks a call signature’ error in TypeScript.
How to fix the ‘Cannot invoke an expression whose type lacks a call signature’ error in TypeScript?
To fix the ‘Cannot invoke an expression whose type lacks a call signature’ error in TypeScript, we can cast the types of the variable so that the TypeScript compiler knows that the types of the object are compatible with the objects we have.
For instance, we write
interface Apple {
color: string;
isDecayed: boolean;
}
interface Pear {
weight: number;
isDecayed: boolean;
}
//...
const freshFruits = (fruits as (Apple | Pear)[]).filter(
(fruit: Apple | Pear) => !fruit.isDecayed
);
to cast the fruits array to type (Apple | Pear)[] so that the TypeScript compiler knows the fruits has objects that are either of type Apple or type Pear.
Likewise, we set the fruit parameter in the callback to Apple | Pear so that the TypeScript compiler knows that fruit is either an Apple or a Pear.
Then we can access the isDecayed property without errors since it’s specified in both interfaces.
Conclusion
To fix the ‘Cannot invoke an expression whose type lacks a call signature’ error in TypeScript, we can cast the types of the variable so that the TypeScript compiler knows that the types of the object are compatible with the objects we have.
