array-last-index-of.js 1.4 KB

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  1. 'use strict';
  2. var toIndexedObject = require('../internals/to-indexed-object');
  3. var toInteger = require('../internals/to-integer');
  4. var toLength = require('../internals/to-length');
  5. var arrayMethodIsStrict = require('../internals/array-method-is-strict');
  6. var arrayMethodUsesToLength = require('../internals/array-method-uses-to-length');
  7. var min = Math.min;
  8. var nativeLastIndexOf = [].lastIndexOf;
  9. var NEGATIVE_ZERO = !!nativeLastIndexOf && 1 / [1].lastIndexOf(1, -0) < 0;
  10. var STRICT_METHOD = arrayMethodIsStrict('lastIndexOf');
  11. // For preventing possible almost infinite loop in non-standard implementations, test the forward version of the method
  12. var USES_TO_LENGTH = arrayMethodUsesToLength('indexOf', { ACCESSORS: true, 1: 0 });
  13. var FORCED = NEGATIVE_ZERO || !STRICT_METHOD || !USES_TO_LENGTH;
  14. // `Array.prototype.lastIndexOf` method implementation
  15. // https://tc39.github.io/ecma262/#sec-array.prototype.lastindexof
  16. module.exports = FORCED ? function lastIndexOf(searchElement /* , fromIndex = @[*-1] */) {
  17. // convert -0 to +0
  18. if (NEGATIVE_ZERO) return nativeLastIndexOf.apply(this, arguments) || 0;
  19. var O = toIndexedObject(this);
  20. var length = toLength(O.length);
  21. var index = length - 1;
  22. if (arguments.length > 1) index = min(index, toInteger(arguments[1]));
  23. if (index < 0) index = length + index;
  24. for (;index >= 0; index--) if (index in O && O[index] === searchElement) return index || 0;
  25. return -1;
  26. } : nativeLastIndexOf;