Array.prototype.includes()

The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.

Syntax

includes(searchElement)
includes(searchElement, fromIndex)

Parameters

• searchElement
  • : The value to search for.
• fromIndex optional
  • : Zero-based index at which to start searching, converted to an integer.
    • Negative index counts back from the end of the array — if fromIndex < 0, fromIndex + array.length is used. However, the array is still searched from front to back in this case.
    • If fromIndex < -array.length or fromIndex is omitted, 0 is used, causing the entire array to be searched.
    • If fromIndex >= array.length, the array is not searched and false is returned.

Return value

A boolean value which is true if the value searchElement is found within the array (or the part of the array indicated by the index fromIndex, if specified).

Description

The includes() method compares searchElement to elements of the array using the SameValueZero algorithm. Values of zero are all considered to be equal, regardless of sign. (That is, -0 is equal to 0), but false is not considered to be the same as 0. NaN can be correctly searched for.

When used on sparse arrays, the includes() method iterates empty slots as if they have the value undefined.

The includes() method is generic. It only expects the this value to have a length property and integer-keyed properties.