Can we prevent an object parameter from being modified in typescript, for example:
interface MyType {
prop1: number
}
function myMethod(param: readonly MyType) {
// How can we make TypeScript give an error here:
param.prop1 = 2
}
Can we prevent an object parameter from being modified in typescript, for example:
interface MyType {
prop1: number
}
function myMethod(param: readonly MyType) {
// How can we make TypeScript give an error here:
param.prop1 = 2
}
To prevent any modifications to the properties of an object, you can utilize the type utility Readonly<Type> as shown below:
interface MyType {
prop1: number;
prop2: number;
}
function myMethod(param: Readonly<MyType>) {
param.prop1 = 2; /*
~~~~~
Cannot assign to 'prop1' because it is a read-only property.(2540) */
param.prop2 = 1; /*
~~~~~
Cannot assign to 'prop2' because it is a read-only property.(2540) */
}
If you only wish to restrict specific properties from being altered, you can label them as read-only using the readonly modifier:
interface MyType {
readonly prop1: number;
prop2: number;
}
function myMethod(param: MyType) {
param.prop1 = 2; /*
~~~~~
Cannot assign to 'prop1' because it is a read-only property.(2540) */
param.prop2 = 1; // ok
}
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