<script>
var n=3.143423423;
alert(n.toString().split(".")[1].length);
</script>
js javascrip 截取小數點後幾位
第一種,利用math.round javascript
var original=28.453
1) //round "original" to two decimals
var result=Math.round(original*100)/100; //returns 28.45
2) // round "original" to 1 decimal
var result=Math.round(original*10)/10; //returns 28.5html
第二種,js1.5以上能夠利用toFixed(x) ,可指定數字截取小數點後 x位java
3) //round "original" to two decimals
var result=original.toFixed(2); //returns 28.45jquery
4) // round "original" to 1 decimal
var result=original.toFixed(1); //returns 28.5git
以上兩種方法最通用,但卻沒法知足某些特殊要求,好比保留小數點後兩位,若是不滿兩位,不滿兩位則補零。此時就有了第三種方法post
1.文本框只能輸入數字代碼(小數點也不能輸入)
<input onkeyup="this.value=this.value.replace(/\D/g,'')" onafterpaste="this.value=this.value.replace(/\D/g,'')">
2.只能輸入數字,能輸小數點.
<input onkeyup="if(isNaN(value))execCommand('undo')" onafterpaste="if(isNaN(value))execCommand('undo')">
<input name=txt1 onchange="if(/\D/.test(this.value)){alert('只能輸入數字');this.value='';}">
3.數字和小數點方法二
<input type=text tvalue="" ovalue="" onkeypress="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" onkeyup="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" onblur="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(/^\.$/))this.value=0;this.ovalue=this.value}">
4.只能輸入字母和漢字
<input onkeyup="value=value.replace(/[\d]/g,'') "onbeforepaste="clipboardData.setData('text',clipboardData.getData('text').replace(/[\d]/g,''))" maxlength=10 name="Numbers">
5.只能輸入英文字母和數字,不能輸入中文
<input onkeyup="value=value.replace(/[^\w\.\/]/ig,'')">
6.只能輸入數字和英文<font color="Red">chun</font>
<input onKeyUp="value=value.replace(/[^\d|chun]/g,'')">
7.小數點後只能有最多兩位(數字,中文均可輸入),不能輸入字母和運算符號:
<input onKeyPress="if((event.keyCode<48 || event.keyCode>57) && event.keyCode!=46 || /\.\d\d$/.test(value))event.returnValue=false">
8.小數點後只能有最多兩位(數字,字母,中文均可輸入),能夠輸入運算符號:
<input onkeyup="this.value=this.value.replace(/^(\-)*(\d+)\.(\d\d).*$/,'$1$2.$3')"> this
JS 方法:<script type="text/javascript">// 獲得字符串的真實長度(雙字節換算爲兩個單字節)function getStrActualLen(sChars){ //sChars.replace(/[^\x00-\xff]/g,"xx").length/1024+"字節"; //Math.round(sChars.replace(/[^\x00-\xff]/g,"xx").length/1024);這個貌似很差使 return alert(formatNum(sChars.replace(/[^\x00-\xff]/g,"xx").length/1024,4));}//格式化小數,並四捨五入。如:formatNum(100.12345678,4) function formatNum(Num1,Num2){ if(isNaN(Num1)||isNaN(Num2)){ return(0); }else{ Num1=Num1.toString(); Num2=parseInt(Num2); if(Num1.indexOf('.')==-1){ return(Num1); }else{ var b=Num1.substring(0,Num1.indexOf('.')+Num2+1); var c=Num1.substring(Num1.indexOf('.')+Num2+1,Num1.indexOf('.')+Num2+2); if(c==""){ return(b); }else{ if(parseInt(c)<5){ return(b); }else{ return((Math.round(parseFloat(b)*Math.pow(10,Num2))+Math.round(parseFloat(Math.pow(0.1,Num2).toString().substring(0,Math.pow(0.1,Num2).toString().indexOf('.')+Num2+1))*Math.pow(10,Num2)))/Math.pow(10,Num2)); } } } } } Jquery方法:function getStrActualLen(){var count=$("#sChars").val().length/1024; return Math.round(count*Math.pow(10,4));}