Array.prototype.indexOf

Returns the index of the first occurrence of a value in an array, or -1 if it is not present.

Syntax

indexOf(value, fromIndex);

Parameters

• value

  The value to locate in the array.

• fromIndex optional

  The array index at which to begin the search. If fromIndex is omitted, the search starts at index 0.

Example

["tea", "coffee", "juice"].indexOf("coffee")

1

["tea", "coffee", "juice"].indexOf("milk")

-1

// returns the first found index
["tea", "coffee", "coffee", "coffee", "juice"].indexOf("coffee")

1

// compare to lastIndexOf:
["tea", "coffee", "coffee", "coffee", "juice"].lastIndexOf("coffee")

3

Return value

An index or -1 if the element was not found.

See also

• lastIndexOf
• findIndex
• find