Equality

Equality helpers

prelude-ts offers some helper functions to implement the equals and hashCode functions for your own objects: fieldsHashCode and areEqual.

Here is an example of object using these helpers:

class MyClass {
    constructor(private field1:string, private field2:number) {}
    equals(other: MyClass): boolean {
        if (!other) {
            return false;
        }
        return areEqual(this.field1, other.field1) &&
            areEqual(this.field2, other.field2);
    }
    hashCode(): number {
        return fieldsHashCode(this.field1, this.field2);
    }
    toString(): string {
        return `{field1: ${this.field1}, field2: ${this.field2}}`;
    }
}

Be careful, equals could be called with a parameter being in fact of another type, so if the field names you compare with are too generic (like id), maybe put a marker to disambiguate the type.

But again, equals and hashCode are not required by prelude.ts, except for Set and Map keys.