带有自定义对象的Typescript数组函数等于

Question

I want to use array functions (like contains, unique) which check equality with my own equals function.

For example:

let arr = [{id:1,..//some more},{id:2,..//some more},{id:3,..//some more}]

I want that this will return true, by using equals function that check the id only:

arr.contains({id:1,....}).

I tried to search by didn't find.

How can I do it? and generally how can I use my own equal function in typescript (like equals function in Java).

Answer 1

You cannot change the equality check used by array functions like includes or indexOf . But other array functions let you use a callback instead:

• find - Finds the first entry in the array for which your callback returns a truthy value
• findIndex - Finds the index of the first entry in the array for which your callback returns a truthy value
• some - Loops through an array calling your callback until it returns a truthy value (in which case some stops and returns true ); if your callback never returns a truthy value, some returns false .
• every - Loops through an array calling your callback until it returns a falsy value (in which case every stops and returns false ); if your callback never returns a falsy value, every returns true .

All of these are described, with linked detailed descriptions, on the MDN array page .

So for example, "contains" with custom equality would be some :

 const a = [ {id: 1}, {id: 2}, {id: 3} ]; console.log("Has 1? " + a.some(e => e.id == 1)); console.log("Has 4? " + a.some(e => e.id == 4)); 

Answer 2

You can use find and test that the value returned is not undefined

Example:

let arr = [{id: 1, test: '1'}, {id: 2, test: '2'}];
const customEqual = i => i.id === 1;
const containsItemWithId1 = arr.find(customEqual) !== undefined;