1.只能输入正整数
<input type="text" onkeyup="if(this.value.length==1){this.value=this.value.replace(/[^1-9]/g,'')}else{this.value=this.value.replace(/\D/g,'')}" onafterpaste="if(this.value.length==1){this.value=this.value.replace(/[^1-9]/g,'')}else{this.value=this.value.replace(/\D/g,'')}" maxlength="8" style="width: 80px"/>
2.只能输入小数并且小数点后最多四位,不能输入符号
<input type="text" onkeyup="num(this)" style="width: 80px"/>
function num(obj){
obj.value = obj.value.replace(/[^\d.]/g,""); //清除"数字"和"."以外的字符
obj.value = obj.value.replace(/^\./g,""); //验证第一个字符是数字
obj.value = obj.value.replace(/\.{2,}/g,"."); //只保留第一个, 清除多余的
obj.value = obj.value.replace(".","$#$").replace(/\./g,"").replace("$#$",".");
obj.value = obj.value.replace(/^(\-)*(\d+)\.(\d\d\d\d).*$/,'$1$2.$3'); //只能输入四个小数
}