<button id="hxjxjs" type="button">元素内文字后加内容</button>
<button id="hxjn" type="button">元素内文字前加内容</button>
<button id="xjswzr" type="button">元素外元素后面加内容</button>
<button id="hxjxjs" type="button">元素内文字后加内容</button>
<button id="hxjn" type="button">元素内文字前加内容</button>
<button id="xjswzr" type="button">元素外元素后面加内容</button>