es.array.splice.js

'use strict';
var $ = require('../internals/export');
var toObject = require('../internals/to-object');
var toAbsoluteIndex = require('../internals/to-absolute-index');
var toIntegerOrInfinity = require('../internals/to-integer-or-infinity');
var lengthOfArrayLike = require('../internals/length-of-array-like');
var setArrayLength = require('../internals/array-set-length');
var doesNotExceedSafeInteger = require('../internals/does-not-exceed-safe-integer');
var arraySpeciesCreate = require('../internals/array-species-create');
var createProperty = require('../internals/create-property');
var deletePropertyOrThrow = require('../internals/delete-property-or-throw');
var arrayMethodHasSpeciesSupport = require('../internals/array-method-has-species-support');

var HAS_SPECIES_SUPPORT = arrayMethodHasSpeciesSupport('splice');

var max = Math.max;
var min = Math.min;

// `Array.prototype.splice` method
// https://tc39.es/ecma262/#sec-array.prototype.splice
// with adding support of @@species
$({ target: 'Array', proto: true, forced: !HAS_SPECIES_SUPPORT }, {
  splice: function splice(start, deleteCount /* , ...items */) {
    var O = toObject(this);
    var len = lengthOfArrayLike(O);
    var actualStart = toAbsoluteIndex(start, len);
    var argumentsLength = arguments.length;
    var insertCount, actualDeleteCount, A, k, from, to;
    if (argumentsLength === 0) {
      insertCount = actualDeleteCount = 0;
    } else if (argumentsLength === 1) {
      insertCount = 0;
      actualDeleteCount = len - actualStart;
    } else {
      insertCount = argumentsLength - 2;
      actualDeleteCount = min(max(toIntegerOrInfinity(deleteCount), 0), len - actualStart);
    }
    doesNotExceedSafeInteger(len + insertCount - actualDeleteCount);
    A = arraySpeciesCreate(O, actualDeleteCount);
    for (k = 0; k < actualDeleteCount; k++) {
      from = actualStart + k;
      if (from in O) createProperty(A, k, O[from]);
    }
    A.length = actualDeleteCount;
    if (insertCount < actualDeleteCount) {
      for (k = actualStart; k < len - actualDeleteCount; k++) {
        from = k + actualDeleteCount;
        to = k + insertCount;
        if (from in O) O[to] = O[from];
        else deletePropertyOrThrow(O, to);
      }
      for (k = len; k > len - actualDeleteCount + insertCount; k--) deletePropertyOrThrow(O, k - 1);
    } else if (insertCount > actualDeleteCount) {
      for (k = len - actualDeleteCount; k > actualStart; k--) {
        from = k + actualDeleteCount - 1;
        to = k + insertCount - 1;
        if (from in O) O[to] = O[from];
        else deletePropertyOrThrow(O, to);
      }
    }
    for (k = 0; k < insertCount; k++) {
      O[k + actualStart] = arguments[k + 2];
    }
    setArrayLength(O, len - actualDeleteCount + insertCount);
    return A;
  }
});