`delete`和Array.splice的区别[JavaScript]

`delete`

delete will delete the object property, but will not reindex the array or update its length. This makes it appears as if it is undefined:

// Array
const myArray = ['a', 'b', 'c', 'd'];
myArray.length  // 4
delete myArray[0];
myArray.length  // 4  不会重新index, 所以length也不会改变

// Note that it is not in fact set to the value undefined, rather the property is removed from the array, making it appear undefined.
myArray[0];   // undefined
// The Chrome dev tools make this distinction clear by printing empty when logging the array.
myArray // [empty, "b", "c", "d"]

但是当delete Object的property时候就没有这个问题：

// Object
const myArray = {'a': 1, 'b': 2, 'c': 3, 'd': 4};
Object.keys(myArray).length // 4
delete myArray['a']
Object.keys(myArray).length // 3

myArray['a'] // undefined
myArray // {b: 2, c: 3, d: 4}

Array.splice

myArray.splice(start, deleteCount) actually removes the element, reindexes the array, and changes its length.
实际上删除元素，重新索引数组，并更改其长度.

> myArray = ['a', 'b', 'c', 'd']
  ["a", "b", "c", "d"]
> myArray.splice(0, 2)
  ["a", "b"]
> myArray
  ["c", "d"]

Array.remove of jQuery

John Resig, creator of jQuery created a very handy Array.remove method that I always use it in my projects.

// Array Remove - By John Resig (MIT Licensed)
Array.prototype.remove = function(from, to) {
  var rest = this.slice((to || from) + 1 || this.length);
  this.length = from < 0 ? this.length + from : from;
  return this.push.apply(this, rest);
};

and here’s some examples of how it could be used:

// Remove the second item from the array
array.remove(1);
// Remove the second-to-last item from the array
array.remove(-2);
// Remove the second and third items from the array
array.remove(1,2);
// Remove the last and second-to-last items from the array
array.remove(-2,-1);