array-concat-spreadable.js (1128B)
1 function testConcat(o1, o2, len, json) { 2 let res = Array.prototype.concat.call(o1, o2); 3 assertEq(res.length, len); 4 assertEq(JSON.stringify(res), json); 5 } 6 7 const o1 = {[Symbol.isConcatSpreadable]: true, length: 2, 0: 4, 1: 5, 2: 6}; 8 const o2 = {[Symbol.isConcatSpreadable]: true, length: 2, 0: 4, 2: 6}; 9 10 testConcat([1, 2, 3], o1, 5, "[1,2,3,4,5]"); 11 testConcat([1, 2, 3], o2, 5, "[1,2,3,4,null]"); 12 13 testConcat(o1, [1, 2, 3], 5, "[4,5,1,2,3]"); 14 testConcat(o2, [1, 2, 3], 5, "[4,null,1,2,3]"); 15 16 testConcat(o1, o1, 4, "[4,5,4,5]"); 17 testConcat(o2, o2, 4, "[4,null,4,null]"); 18 19 testConcat(o1, o2, 4, "[4,5,4,null]"); 20 testConcat(o2, o1, 4, "[4,null,4,5]"); 21 22 o1[Symbol.isConcatSpreadable] = false; 23 24 testConcat(o1, o2, 3, '[{"0":4,"1":5,"2":6,"length":2},4,null]'); 25 testConcat(o2, o1, 3, '[4,null,{"0":4,"1":5,"2":6,"length":2}]'); 26 27 const ta = new Int32Array([4, 5, 6]); 28 testConcat([1, 2, 3], ta, 4, '[1,2,3,{"0":4,"1":5,"2":6}]'); 29 testConcat(ta, ta, 2, '[{"0":4,"1":5,"2":6},{"0":4,"1":5,"2":6}]'); 30 31 ta[Symbol.isConcatSpreadable] = true; 32 testConcat([1, 2, 3], ta, 6, "[1,2,3,4,5,6]"); 33 testConcat(ta, ta, 6, "[4,5,6,4,5,6]");