From c0665b0336cf260f7583d24af3ca911e4fb123c7 Mon Sep 17 00:00:00 2001 From: Gal Schlezinger Date: Tue, 19 Mar 2019 10:29:52 +0200 Subject: [PATCH] Generic type-safe implementation for Object.assign It seems that it can be possible to make a type-safe `Object.assign`-like functions with TypeScript, without having to make lots of overrides. Here's an example on the playground: typescriptlang.org/play/index.html#src=function%20assign%3CSource%20extends%20%7B%7D%2C%20Result%20extends%20Source%3E(%0D%0A%20%20%20%20target%3A%20Source%2C%0D%0A%20%20%20%20...sources%3A%20Source%5B%5D%0D%0A)%3A%20Pick%3CResult%2C%20keyof%20Source%3E%20%7B%0D%0A%20%20%20%20return%20Object.assign(target%2C%20...sources)%3B%0D%0A%7D%0D%0A%0D%0Alet%20x%20%3D%0D%0A%20%20%20%20assign(%0D%0A%20%20%20%20%20%20%20%20%7B%20hello%3A%20%22world%22%20%7D%2C%0D%0A%20%20%20%20%20%20%20%20%7B%20something%3A%20%22is%20good%22%20%7D%2C%0D%0A%20%20%20%20%20%20%20%20%7B%20%22yes%22%3A%20true%20%7D%2C%0D%0A%20%20%20%20%20%20%20%20%7B%20yes%3A%20%22hello%22%20%7D%0D%0A%20%20%20%20)%3B%0D%0A%0D%0Ax.hello%3B%0D%0Ax.world%3B%20%2F%2F%20error!%0D%0Ax.yes%3B You can see that the compiler says `x.hello` is fine, and complains about `x.world` --- src/lib/es2015.core.d.ts | 31 ++----------------------------- 1 file changed, 2 insertions(+), 29 deletions(-) diff --git a/src/lib/es2015.core.d.ts b/src/lib/es2015.core.d.ts index cfb300c784d74..77efa9273bf69 100644 --- a/src/lib/es2015.core.d.ts +++ b/src/lib/es2015.core.d.ts @@ -261,36 +261,9 @@ interface ObjectConstructor { * Copy the values of all of the enumerable own properties from one or more source objects to a * target object. Returns the target object. * @param target The target object to copy to. - * @param source The source object from which to copy properties. + * @param sources The source objects from which to copy properties. */ - assign(target: T, source: U): T & U; - - /** - * Copy the values of all of the enumerable own properties from one or more source objects to a - * target object. Returns the target object. - * @param target The target object to copy to. - * @param source1 The first source object from which to copy properties. - * @param source2 The second source object from which to copy properties. - */ - assign(target: T, source1: U, source2: V): T & U & V; - - /** - * Copy the values of all of the enumerable own properties from one or more source objects to a - * target object. Returns the target object. - * @param target The target object to copy to. - * @param source1 The first source object from which to copy properties. - * @param source2 The second source object from which to copy properties. - * @param source3 The third source object from which to copy properties. - */ - assign(target: T, source1: U, source2: V, source3: W): T & U & V & W; - - /** - * Copy the values of all of the enumerable own properties from one or more source objects to a - * target object. Returns the target object. - * @param target The target object to copy to. - * @param sources One or more source objects from which to copy properties - */ - assign(target: object, ...sources: any[]): any; + assign(target: Source, ...sources: Source[]): Pick; /** * Returns an array of all symbol properties found directly on object o.