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- 'use strict';
- var $ = require('../internals/export');
- var toObject = require('../internals/to-object');
- var lengthOfArrayLike = require('../internals/length-of-array-like');
- var setArrayLength = require('../internals/array-set-length');
- var deletePropertyOrThrow = require('../internals/delete-property-or-throw');
- var doesNotExceedSafeInteger = require('../internals/does-not-exceed-safe-integer');
-
- // IE8-
- var INCORRECT_RESULT = [].unshift(0) !== 1;
-
- // V8 ~ Chrome < 71 and Safari <= 15.4, FF < 23 throws InternalError
- var properErrorOnNonWritableLength = function () {
- try {
- // eslint-disable-next-line es/no-object-defineproperty -- safe
- Object.defineProperty([], 'length', { writable: false }).unshift();
- } catch (error) {
- return error instanceof TypeError;
- }
- };
-
- var FORCED = INCORRECT_RESULT || !properErrorOnNonWritableLength();
-
- // `Array.prototype.unshift` method
- // https://tc39.es/ecma262/#sec-array.prototype.unshift
- $({ target: 'Array', proto: true, arity: 1, forced: FORCED }, {
- // eslint-disable-next-line no-unused-vars -- required for `.length`
- unshift: function unshift(item) {
- var O = toObject(this);
- var len = lengthOfArrayLike(O);
- var argCount = arguments.length;
- if (argCount) {
- doesNotExceedSafeInteger(len + argCount);
- var k = len;
- while (k--) {
- var to = k + argCount;
- if (k in O) O[to] = O[k];
- else deletePropertyOrThrow(O, to);
- }
- for (var j = 0; j < argCount; j++) {
- O[j] = arguments[j];
- }
- } return setArrayLength(O, len + argCount);
- }
- });
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