Array

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

Name	Type	Description
valueN	Array	Arrays and/or values to concatenate into a new array. If all valueN parameters are omitted, concat returns a shallow copy of the existing array on which it is called. See the description below for more details.

A new Array instance.

The copyWithin() method shallow copies part of an array to another location in the same array and returns it without modifying its length.

Name	Type	Description
target	Array	Zero-based index at which to copy the sequence to. If negative, target will be counted from the end.
start	Number	Zero-based index at which to start copying elements from. If negative, start will be counted from the end.
end	Number	Zero-based index at which to end copying elements from. copyWithin copies up to but not including end. If negative, end will be counted from the end.

The modified array.

The entries() method returns a new Array Iterator object that contains the key/value pairs for each index in the array.

A new Array iterator object.

The every() method tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value.

Name	Type	Description
callback	Object	A function to test for each element, taking three arguments: element, index, array
thisArg	Object	A value to use as this when executing callback

true if the callback function returns a truthy value for every array element. Otherwise, false.