set-length-sparse-2.js

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function testDenseAndSparse1() {

  var arr = [1, 2, 3, 4, 5];

  arr[2000000] = 2;

  arr[1000000] = 1;

  assertEq(arr.length, 2000001);

  arr.length = 1500000;

  assertEq(Object.keys(arr).length, 6);

  arr.length = 2;

  assertEq(Object.keys(arr).length, 2);

  assertEq(JSON.stringify(arr), "[1,2]");

testDenseAndSparse1();

function testDenseAndSparse2() {

  var arr = [1, 2, 3, 4, 5, 6];

  Object.defineProperty(arr, 1, {configurable: true, writable: false, value: -2});

  Object.defineProperty(arr, 3, {configurable: true, get: () => -4});

  assertEq(JSON.stringify(arr), "[1,-2,3,-4,5,6]");

  arr.length = 4;

  assertEq(Object.keys(arr).length, 4);

  assertEq(JSON.stringify(arr), "[1,-2,3,-4]");

  arr.length = 3;

  assertEq(Object.keys(arr).length, 3);

  assertEq(JSON.stringify(arr), "[1,-2,3]");

  arr.length = 2;

  assertEq(Object.keys(arr).length, 2);

  assertEq(JSON.stringify(arr), "[1,-2]");

  arr.length = 1;

  assertEq(Object.keys(arr).length, 1);

  assertEq(JSON.stringify(arr), "[1]");

  arr.length = 0;

  assertEq(Object.keys(arr).length, 0);

  assertEq(JSON.stringify(arr), "[]");

  arr[0] = 11;

  arr[1] = 22;

  arr[2] = 33;

  assertEq(Object.keys(arr).length, 3);

  assertEq(JSON.stringify(arr), "[11,22,33]");

testDenseAndSparse2();