多项选择题
A.const cat = {lives: 9,jumps: () => { this.lives--; }} ；
B.var button = document.getElementById('press');button.addEventListener('click', () => {this.classList.toggle('on');}); ；
C.let insert = (value) => ({into: (array) => ({after: (afterValue) => { array.splice(array.indexOf(afterValue) + 1, 0, value);return array;}})});
D.const mult2 = a => a * 2;