在没有内置函数的情况下删除 JavaScript 数组项？

Question

How can I remove an item from a JavaScript array without using built in functions like pop() and splice()?

Answer 1

You can use Array rest parameter and destructuring for that

if you want to delete something from beginning

 let arr = [1, 2, 3, 4]; let [c, d, ...newarr] = arr; console.log(newarr)

Answer 2

If you don't care about the array being reindexed, you can use the delete operator , but it will leave an undefined entry where the deleted value was, and the .length of the array will still be the same as before:

 const arr = [1, 2, 3, 4, 5]; console.log(arr.length, `[${ arr.join(', ') }]`); delete arr[2]; console.log(arr.length, `[${ arr.join(', ') }]`);

If you want to delete elements from the end, you can manually update the .length property of the array:

 const arr = [1, 2, 3, 4, 5]; console.log(arr.length, `[${ arr.join(', ') }]`); arr.length = 3;; console.log(arr.length, `[${ arr.join(', ') }]`);

Otherwise, you can use a loop to go through the original elements and push the ones you want to keep to a separate array:

 const arr = [1, 2, 3, 4, 5]; console.log(arr.length, `[${ arr.join(', ') }]`); const even = []; for (let n of arr) { if (n % 2 === 0) even.push(n); } console.log(even.length, `[${ even.join(', ') }]`);

Answer 3

You can use slice

const arr = [1,2,3,4,5];
console.log(arr.slice(0,4));  // [1,2,3,4];
console.log(arr.slice(1,5));  // [2,3,4,5];

Answer 4

Thanks to Paul in the comment section for suggesting arr.length--; . Since I was using pop() previously the item I wanted to remove was already at the end so it worked out perfectly.

Answer 5

You could create your own method like below:

Array.prototype.removeItem = function(item) {
    for (i = 0; i < this.length; i++) {
        if (this[i] === item) {
            for (var j = i; j < this.length - 1; j++) {
                this[j] = this[j + 1];
            }
            this.length = this.length - 1
            return;
        }
    }
}

var items = ['a', 'b', 'c', 'd'];
items.removeItem('c');