1. JS 判断字符串是否全部为字母
val = "123456" var isletter = /^[a-zA-Z]+$/.test(val); document.write(isletter);//false document.write("<br>"); val2 = "asaaa" var isletter2 = /^[a-zA-Z]+$/.test(val2); document.write(isletter2);//true
2.JS 判断字符串是否全部为数字
val = "123456" var isnum = /^\d+$/.test(val); document.write(isnum);//true document.write("<br>"); val2 = "as123" var isnum2 = /^\d+$/.test(val2); document.write(isnum2);//false
3.JS 判断输入是否为数字、字母、下划线组成
function isValid(str) { return /^\w+$/.test(str); } str = "1234abd__" document.write(isValid(str));//true document.write("<br>"); str2 = "$32343#" document.write(isValid(str2));//false document.write("<br>");