_.lastIndexOf

Returns the index of the last occurrence of value in the array, or -1 if value is not present.

// Underscore/Lodash
var array = [2, 9, 9, 4, 3, 6]
var result = _.lastIndexOf(array, 9)
console.log(result)
// output: 2
 
// Native
var array = [2, 9, 9, 4, 3, 6]
var result = array.lastIndexOf(9)
console.log(result)
// output: 2

Browser Support for Array.prototype.lastIndexOf()

✔	✔	1.5 ✔	9.0 ✔	✔	✔