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Suguru Inatomi
Suguru Inatomi

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Merging objects with Partial type

My usual implementation pattern of immutable merging in TypeScript.

class MyClass {
    constructor(public id: string, public name: string) {}

    clone() {
        return new MyClass(,;

    merge(another: Partial<MyClass>) {
        return Object.assign(this.clone(), another);

const objA = new MyClass("1", "foo");

const objB = objA.merge({ name: "bar" });

console.log(objA !== objB);
console.log( === "1");
console.log( === "bar");
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Partial<MyClass> allows us to pass an object matching MyClass partially.

Oldest comments (0)


11 Tips That Make You a Better Typescript Programmer

1 Think in {Set}

Type is an everyday concept to programmers, but it’s surprisingly difficult to define it succinctly. I find it helpful to use Set as a conceptual model instead.

#2 Understand declared type and narrowed type

One extremely powerful typescript feature is automatic type narrowing based on control flow. This means a variable has two types associated with it at any specific point of code location: a declaration type and a narrowed type.

#3 Use discriminated union instead of optional fields


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