应该是这句的问题，obj.style.height = ((this.state == "down") ? (h + 2) : (h - 2))+"px"; 我的测试环境是IE6，在(h-2)最终会出现负值。改成这样就行了：obj.style.height = ((this.state == "down") ? (h + 2) : ((h - 2) < 0 ? 0:(h - 2)))+"px";
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