es.array.unshift.js 1.5 KB

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  1. 'use strict';
  2. var $ = require('../internals/export');
  3. var toObject = require('../internals/to-object');
  4. var lengthOfArrayLike = require('../internals/length-of-array-like');
  5. var deletePropertyOrThrow = require('../internals/delete-property-or-throw');
  6. var doesNotExceedSafeInteger = require('../internals/does-not-exceed-safe-integer');
  7. // IE8-
  8. var INCORRECT_RESULT = [].unshift(0) !== 1;
  9. // V8 ~ Chrome < 71 and Safari <= 15.4, FF < 23 throws InternalError
  10. var SILENT_ON_NON_WRITABLE_LENGTH = !function () {
  11. try {
  12. // eslint-disable-next-line es-x/no-object-defineproperty -- safe
  13. Object.defineProperty([], 'length', { writable: false }).unshift();
  14. } catch (error) {
  15. return error instanceof TypeError;
  16. }
  17. }();
  18. // `Array.prototype.unshift` method
  19. // https://tc39.es/ecma262/#sec-array.prototype.unshift
  20. $({ target: 'Array', proto: true, arity: 1, forced: INCORRECT_RESULT || SILENT_ON_NON_WRITABLE_LENGTH }, {
  21. // eslint-disable-next-line no-unused-vars -- required for `.length`
  22. unshift: function unshift(item) {
  23. var O = toObject(this);
  24. var len = lengthOfArrayLike(O);
  25. var argCount = arguments.length;
  26. if (argCount) {
  27. doesNotExceedSafeInteger(len + argCount);
  28. var k = len;
  29. while (k--) {
  30. var to = k + argCount;
  31. if (k in O) O[to] = O[k];
  32. else deletePropertyOrThrow(O, to);
  33. }
  34. for (var j = 0; j < argCount; j++) {
  35. O[j] = arguments[j];
  36. }
  37. } return O.length = len + argCount;
  38. }
  39. });