Summary of methods to use JS to determine whether a string contains numbers and special characters

Foreword

This article mainly introduces the method of using JS to determine whether a string contains numbers and special characters. There are several different methods in the article, including ordinary JS verification method, regular expression method, and also judging whether it is a float. Points js function, at the end we will briefly introduce the usage and examples of isNAN function, let’s learn together.

1. Regular expression method to determine whether it is a number, including determining positive integer:

function checkRate(input)
{
 var re = /^[0-9]+.?[0-9]*$/; //判断字符串是否为数字,//若判断正整数，则后边是：/^[1-9]+[0-9]*]*$/
 if (!re.test(input.rate.value))
 {
 alert("请输入数字(例:0.02)");
 input.rate.focus();
 return false;
 }
}

2. Ordinary JS function method:

function BASEisNotNum(theNum)
{
if (BASEtrim(theNum)=="")
return true;
for(var i=0;i<theNum.length;i++){
oneNum=theNum.substring(i,i+1);
if (oneNum<"0" || oneNum>"9")
return true;
}
return false;
}

3. Determine whether it is a positive number, that is Positive integer:

function BASEisNotInt(theInt)
{
theInt=BASEtrim(theInt);
if ((theInt.length>1 && theInt.substring(0,1)=="0") || BASEisNotNum(theInt)){
return true;
}
return false;
}

4. Determine whether the string is composed of numbers and other symbols, such as "-":

function ismonth(str)
{
for(ilen=0;ilen<str.length;ilen++)
{
if(str.charAt(ilen) < &#39;0&#39; || str.charAt(ilen) > &#39;9&#39; )
{
if((str.charAt(ilen)!=&#39;-&#39;))
return false;
}
}
return true;
}

5. Determine whether it is a floating point number:

function BASEisNotFloat(theFloat)
{
len=theFloat.length;
dotNum=0;
if (len==0)
return true;
for(var i=0;i<len;i++){
oneNum=theFloat.substring(i,i+1);
if (oneNum==".")
dotNum++;
if ( ((oneNum<"0" || oneNum>"9") && oneNum!=".") || dotNum>1)
return true;
}
if (len>1 && theFloat.substring(0,1)=="0"){
if (theFloat.substring(1,2)!=".")
return true;
}
return false;

About the isNaN function of javascript: Usage rules: isNaN(expression:Object): Boolean. Computes a parameter and returns true if the value is NaN (not a number). This function can be used to check whether a mathematical expression evaluates successfully to a number.

Availability: Flash Player 5; ActionScript 1.0; Parameter expression: Object - Boolean value, variable or other expression to be evaluated. Returns Boolean - Boolean value.

is often used like this in submission forms:

<script>
if(isNaN(document.login.imgcode.value)){
alert(&#39;验证码不是数字！&#39;)
document.login.imgcode.focus();
return false;
}
</script>