core-js/library/modules/es6.array.last-index-of.js

Standard library

'use strict';
var $export   = require('./_export')
  , toIObject = require('./_to-iobject')
  , toInteger = require('./_to-integer')
  , toLength  = require('./_to-length');

$export($export.P + $export.F * !require('./_strict-method')([].lastIndexOf), 'Array', {
  // 22.1.3.14 / 15.4.4.15 Array.prototype.lastIndexOf(searchElement [, fromIndex])
  lastIndexOf: function lastIndexOf(searchElement /*, fromIndex = @[*-1] */){
    var O      = toIObject(this)
      , length = toLength(O.length)
      , index  = length - 1;
    if(arguments.length > 1)index = Math.min(index, toInteger(arguments[1]));
    if(index < 0)index = length + index;
    for(;index >= 0; index--)if(index in O)if(O[index] === searchElement)return index;
    return -1;
  }
});