Array#indexOf(item[, offset = 0]) → Number

• item (?) – A value that may or may not be in the array.
• offset (Number) – The number of initial items to skip before beginning the search.

Returns the index of the first occurrence of item within the array, or -1 if item doesn't exist in the array. Array#indexOf compares items using strict equality (===).

Examples

[3, 5, 6, 1, 20].indexOf(1)
// -> 3
 [3, 5, 6, 1, 20].indexOf(90)
// -> -1 (not found)
 ['1', '2', '3'].indexOf(1);
// -> -1 (not found, 1 !== '1')