如果<button>标签在<form>中不加type=“button”，那么默认含义是“submit”。
<button>标签里面disabled属性使其不可用，常见javascript修改disabled属性实例：（a键b键互相撕逼）
<style>#a,#b{height:30px;width:70px;background:yellow;box-sizing:border-box；}</style></head><body><button type="button" id="a" οnclick="an()" >会变色</button><button type="button" id="b" οnclick="bn()" >会变色</button><script>function bn(){if(document.getElementById("b").disabled!="true"){document.getElementById("b").disabled="true";document.getElementById("b").style.background="gray";document.getElementById("a").removeAttribute("disabled");document.getElementById("a").removeAttribute("style");}else{document.getElementById("a").disabled="true";document.getElementById("a").style.background="gray";document.getElementById("b").removeAttribute("disabled");document.getElementById("b").removeAttribute("style");}}function an(){if(document.getElementById("a").disabled!="true"){document.getElementById("a").disabled="true";document.getElementById("a").style.background="gray";document.getElementById("b").removeAttribute("disabled");document.getElementById("b").removeAttribute("style");}else{document.getElementById("b").disabled="true";document.getElementById("b").style.background="gray";document.getElementById("a").removeAttribute("disabled");document.getElementById("a").removeAttribute("style");}}</script></body>
