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If you do not specify any elements, splice() will only remove elements from the array. The elements to add to the array, beginning from start. In this case, you should specify at least one new element (see below). If deleteCount is 0 or negative, no elements are removed. However, if you wish to pass any itemN parameter, you should pass Infinity as deleteCount to delete all elements after start, because an explicit undefined gets converted to 0. All built-in array-copy operations (spread syntax, om(), (), and ()) create shallow copies. slice returns a sub-set of the original array, with the original array remaining untouched. If deleteCount is omitted, or if its value is greater than or equal to the number of elements after the position specified by start, then all the elements from start to the end of the array will be deleted. An important consideration relating to the answer by insomniac is that splice and slice are two completely different functions, with the main difference being: splice manipulates the original array. This is different from passing undefined, which is converted to 0.Īn integer indicating the number of elements in the array to remove from start. If start is omitted (and splice() is called with no arguments), nothing is deleted.This can be negative also, which begins after many elements counting from. This parameter is the index from which the modification of the array starts (with the origin at 0).

Negative index counts back from the end of the array - if start = array.length, no element will be deleted, but the method will behave as an adding function, adding as many elements as provided. Syntax: Array.splice ( index, removecount, itemlist ) Parameter: This method accepts many parameters some of which are described below: index: It is a required parameter.Zero-based index at which to start changing the array, converted to an integer. 'b' So, in summary use delete on object literals. Finally, if you want to remove an element from an array.

Object.prototype._lookupSetter_() Deprecated The element index is preserved and the value is set to 'undefined' Conversely, performing a delete on an object literal removes the key/value from the object.

To access part of an array without modifying it, see slice (). To create a new array with a segment removed and/or replaced without mutating the original array, use toSpliced ().

Object.prototype._lookupGetter_() Deprecated The splice () method of Array instances changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

The final result of running the reducer across all elements of the array is a single value.

Object.prototype._defineSetter_() Deprecated () The reduce () method of Array instances executes a user-supplied 'reducer' callback function on each element of the array, in order, passing in the return value from the calculation on the preceding element.

What you are actually seeing, is the return value of splice method, which is an array containing the removed elements, which in both your method calls, are none.

Object.prototype._defineGetter_() Deprecated All other answers correctly describe splice method and spread operator behavior, but none tries to correct your misunderstanding about the result.