on><input type="checkbox">榴莲</button>
			<button><input type="checkbox">西瓜</button>
			<button><input type="checkbox">芒果</button>
			<button><input type="checkbox">柠檬</button>
		</div>
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			var buttons = document.querySelectorAll('#buttons>button');
			for (var i = 0; i < buttons.length; i += 1) {
				buttons[i].firstChild.addEventListener('click', function(evt) {
					var checkbox = evt.target || evt.srcElement;
					if (checkbox.checked) {
						checkbox.parentNode.style.backgroun