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JavaScript validation is a numerical method summary

Source: Internet
Author: User
Tags numeric
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isNaN function
isNaN (expression:object): Boolean

Evaluates the argument and returns True if the value is NaN (non-numeric). This function can be used to check whether a mathematical expression was successfully evaluated as a number.


The isNaN function is as follows:

The code is as follows Copy Code

function Checknum (str) {
if (isNaN (str)) {
Alert ("Not a number");
}
}

See Also

The code is as follows Copy Code

parseint ("Hello");//return NAN
parseint ("//return"); 110

So the simple way to judge whether a string is a number is to take advantage of isNaN (), and if true, the string is not a number, otherwise it is a number

The code is as follows Copy Code

isNaN (parseint ("Hello"));//true;
isNaN ("parseint");//false;

Note: The following methods cannot be used to determine:

The code is as follows Copy Code

parseint ("Hello", ten) ==nan;//return false
parseint ("==nan;//return") false

In addition, you can use regular expressions, the most complete and most accurate method:

The code is as follows Copy Code

function Isnumber (onum)
{
if (!onum) return false;
var strp=/^d+ (. d+)? $/;
if (!strp.test (Onum)) return false;
try{
if (parsefloat (onum)!=onum) return false;
}
catch (ex)
{
return false;
}
return true;
}

This JavaScript code is very concise, you can see.

The code is as follows Copy Code
<script language=javascript>
function Onlynum ()
{
if (!) ( (event.keycode>=48&&event.keycode<=57) | | (event.keycode>=96&&event.keycode<=105)))
Consider the number keys on the keypad
Event.returnvalue=false;
}
</script>
<input onkeydown= "Onlynum ();" >

There is a more stupid way, we can also see, study
The next time you stick with a regular validation number

The code is as follows Copy Code
<script language= "JavaScript" >
function Checkmyform ()
{
var txt = myform.mytext.value;
if (CheckNumber (TXT))
{
Alert ("Only allow numbers to be entered!") ");
return false;
}
return true;
}
function CheckNumber (String)
{
var letters = "1234567890";
var i;
var C;
for (i = 0; i < string.length i + +)
{
c = String.charat (i);
if (Letters.indexof (c) ==-1)
{
return true;
}
}
return false;
}
</script>
<body>
<form name= "MyForm" onsubmit= "return Checkmyform ()" >
<input type= "text" name= "MyText" >
<input type= "Submit" Name= "Mysubmit" >
</form>
</body>

The simplest JavaScript validation is not a number code as follows:

The code is as follows Copy Code

<input type= ' TEXT ' onkeypress= ' if (event.keycode==13) {if (isNaN (this.value)) alert (' Not numeric ')}; >

Regular numeric expressions used in common use

1)

The code is as follows Copy Code

"^\d+$"//non-negative Integer (positive integer + 0)
"^[0-9]*[1-9][0-9]*$"//Positive integer
"^ ((-\d+) | (0+)) $ "//non-positive integer (negative integer + 0)
"^-[0-9]*[1-9][0-9]*$"//Negative integer
"^-?\d+$"//Integer
"^\d+ ()//nonnegative floating-point number (positive floating-point number + 0)
"^ ([0-9]+\. [0-9]*[1-9][0-9]*) | ([0-9]*[1-9][0-9]*\. [0-9]+) | ([0-9]*[1-9][0-9]*)] $ "//Positive floating-point number
"^ ((-\d+ ()//non-positive floating-point number (negative floating-point number + 0)
^ (-([0-9]+\. [0-9]*[1-9][0-9]*) | ([0-9]*[1-9][0-9]*\. [0-9]+) | ([0-9]*[1-9][0-9]*))] $ "//negative floating-point number
"^ (-?\d+) ("//floating-point number

2)

  code is as follows copy code

var r =/^+?[ 1-9][0-9]*$/; Positive integer
R.test (str);

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Related Keywords:
w3schools javascript form validation javascript form validation php javascript inline form validation textbox validation in javascript javascript file type validation javascript validation library email validation regex javascript
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