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

Standard library

'use strict';
var $export  = require('./_export')
  , $indexOf = require('./_array-includes')(false);

$export($export.P + $export.F * !require('./_strict-method')([].indexOf), 'Array', {
  // 22.1.3.11 / 15.4.4.14 Array.prototype.indexOf(searchElement [, fromIndex])
  indexOf: function indexOf(searchElement /*, fromIndex = 0 */){
    return $indexOf(this, searchElement, arguments[1]);
  }
});