<!DOCTYPE html><html><head><meta charset="utf-8"><title></title></head><body><input type="text" id="abc" onblur="a2A()"><script>function a2A() {// 获取id为abc的value值var abc = document.getElementById("abc").value;// 正则表达式规定只能大小写a-z确保都是字母var abcReg =/^[a-zA-Z]+$/// test判断if (abcReg.test(abc)) {document.getElementById("abc").value = document.getElementById("abc").value.toUpperCase()} else {alert("请输入正确的字母")}}</script></body></html>
