Passing an array of unknown shape-CodePudding

I have a simple function that I use to duplicate an array:

const data = (items) => {
  myData = items.slice()
}

Now items is an array of objects and these objects can be of any shape. How do I achieve this in TypeScript?

const data = (items: Array<any>) => {

This works but I am not sure if using any here is the best way.

CodePudding user response：

You can achieve this by using generics, which will allow you to infer the input type

In the following example, I return the copy for demonstration purpose, so you can see what's inferred for the output given T

// T extends unknown restricts[] the parameters to be of array type
const data = <T extends unknown[]>(items: T): T => {
  myData = items.slice()
  return myData;
}

// inferred as number[]
const outputA = data([1, 2, 3])

// inferred as string[]
cont outputB = data(['str1', 'str2'])

CodePudding user response：

You didn't specify what myData is and how you want to use it. I guess you want that function to return the copied array? In that case you can add a generic to data so the type of the returned array gets inferred from what you pass as a parameter.

const data = <T,>(items: T[]): T[] => {
    return items.slice()
}

const newArray = data([3,4,5])
// const newArray: number[]

playground link

CodePudding user response：

The other answers are really good, but I don't like them for more complex objects since I don't think they do a deep copy, but this does it :

const a = (items: any[]): any[] => {
    const copyArray: any[] = []
    items.forEach((i) => copyArray.push({...i}));
    return copyArray;
}

const a = (items: any[]): any[] => {
    const copyArray: any[] = []
    items.forEach((i) => copyArray.push(Object.assign({}, i)));
    return copyArray;
}

Unfortunately for list strings it's not the best since it will split them into arrays.

playground