Question

Technologies:

javascript

typescript

Tolerim

5 hours ago

How can I use Object.assign without getting the TS2556 error that says a spread argument has to be a tuple type or passed to a rest parameter?

In this code snippet, there is a function called "getObjectFromTwoArrays" that takes in two arrays and maps the values to create a new object. The "StartPoint" shows the input arrays, while the "EndPoint" shows the desired object output. However, attempts to modify the code by assigning the result to a variable or using different syntaxes did not yield the correct output. How can we get the desired "EndPoint" object as the result of this function?

Answers(1)

Accepted Answer

The issue with the attempted solutions using the spread syntax and array notation is that they are not creating the desired object structure. Instead, the map function is returning an array of objects with the desired key-value pairs, but Object.assign is not combining them into a single object as intended. To get the desired result of an object with the key-value pairs corresponding to the input arrays, the original solution using Object.assign with a spread and map is correct. However, the error being thrown when the input arrays are not the same length could be made more helpful by including the actual lengths of the arrays in the message. Here is the corrected code:

export default function getObjectFromTwoArrays(keyArr: Array<any>, valueArr: Array<any>) {
  // StartPoint:
  //  [key1,key2,key3],
  //  [value1,value2,value3]
  //
  // EndPoint: {
  //  key1: value1,
  //  key2: value2,
  //  key3: value3
  // }

  if (keyArr.length === valueArr.length) {
    return Object.assign({}, ...keyArr.map((el,index) => ({[el]: valueArr[index]})))
  } else {
    throw new Error(`Arrays should be the same length: ${keyArr.length}, ${valueArr.length}`)
  }
}

Note that the empty object passed as the first argument to Object.assign is necessary to avoid modifying any existing objects and instead create a new one with the combined properties.