从数组中删除元素（拼接）

Question

Basic question on .splice() method, and how best to remove an element from an array.

I want to remove an item from an array with .splice() but when I do, I want to have the original array minus the removed element returned. .splice() returns the removed element instead.

var arr = [1, 2, 3, 4, 5, 6, 7]
var newArr = arr.splice(3, 1)

console.log(newArr) // [4]

// whereas I want [1, 2, 3, 5, 6, 7]

What's the best, and most eloquent way to do this?

Answer 1

Using the spread operator, you can do:

var arr = [1,2,3,4,5,6],
    indexToRemove = 3,
    newArr = [
      ...arr.slice(0,indexToRemove),
      ...arr.slice(indexToRemove+1)
    ]

Or if you want to use ES5, it can look something like:

var arr = [1,2,3,4,5,6],
    indexToRemove = 3,
    newArr = [].concat(arr.slice(0,indexToRemove)).concat(arr.slice(indexToRemove+1))

Answer 2

.splice mutates the array in place and returns the removed elements. So unless you actually need a function that returns the array itself, just access arr :

var arr = [1, 2, 3, 4, 5, 6, 7]
arr.splice(3, 1)
console.log(arr) //  [1, 2, 3, 5, 6, 7]

---

You can create a wrapper function that performs the splice and returns the array:

function remove(arr, index) {
  arr.splice(index, 1)
  return arr;
}

var newArr = remove(arr, 3);
// Note: `newArr` is not a new array, it has the same value as `arr`

---

If you want to create a new array , without mutating the original array, you could use .filter :

var newArr = arr.filter(function(element, index) {
  return index !== 3;
}); // [1, 2, 3, 5, 6, 7]
arr; // [1, 2, 3, 4, 5, 6, 7]