JS判断只能是数字和小数点 1.文本框只能输入数字代码(小数点也不能输入) <input οnkeyup="this.value=this.value.replace(/\D/g,'')" onafterpaste="this.value=this.value.replace(/\D/g,'')"> 2.只能输入数字,能输小数点. 
<input οnkeyup="if(isNaN(value))execCommand('undo')" onafterpaste="if(isNaN(value))execCommand('undo')"> 
<input name=txt1 οnchange="if(/\D/.test(this.value)){alert('只能输入数字');this.value='';}"> 3.数字和小数点方法二 
<input type=text tvalue="" ovalue="" οnkeypress="if(!this.value.match(/^[\+\-]?\d*?\.?\d*?$/))this.value=this.t_value;else this.tvalue=this.value;if(this.value.match(/^(?:[\+\-]?\d+(?:\.\d+)?)?$/))this.ovalue=this.value" οnkeyup="if(!this.value.match(/^[\+\-]?\d*?\.?\d*?$/))this.value=this.t_value;else this.tvalue=this.value;if(this.value.match(/^(?:[\+\-]?\d+(?:\.\d+)?)?$/))this.ovalue=this.value" οnblur="if(!this.value.match(/^(?:[\+\-]?\d+(?:\.\d+)?|\.\d*?)?$/))this.value=this.o_value;else{if(this.value.match(/^\.\d+$/))this.value=0+this.value;if(this.value.match(/^\.$/))this.value=0;this.ovalue=this.value}">4.只能输入字母和汉字 <input οnkeyup="value=value.replace(/[\d]/g,'') "onbeforepaste="clipboardData.setData('text',clipboardData.getData('text').replace(/[\d]/g,''))" maxlength=10 name="Numbers"> 5.只能输入英文字母和数字,不能输入中文 
<input οnkeyup="value=value.replace(/[^\w\.\/]/ig,'')"> 6.只能输入数字和英文<font color="Red">chun</font> 
<input onKeyUp="value=value.replace(/[^\d|chun]/g,'')"> 7.小数点后只能有最多两位(数字,中文都可输入),不能输入字母和运算符号: 
<input onKeyPress="if((event.keyCode<48 || event.keyCode>57) && event.keyCode!=46 || /\.\d\d$/.test(value))event.returnValue=false"> 8.小数点后只能有最多两位(数字,字母,中文都可输入),可以输入运算符号: 
<input οnkeyup="this.value=this.value.replace(/^(\-)*(\d+)\.(\d\d).*$/,'$1$2.$3')"> 
只能是数字和小数点和加减乘际

οnkeypress="return event.keyCode>=4&&event.keyCode<=57"