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Checking number using isNaN function
JavaScript has one important function isNaN() to check any data is number or string. This function isNaN() is remembered as short form is Is Not a Number. This function returns true if the data is string and returns false if the data is a number. Here is one simple example to check one string. We will use one if else condition check to display a message accordingly. Here is the code.
var my_string="This is a string";
if(isNaN(my_string)){
document.write ("this is not a number ");
}else{document.write ("this is a number ");
}
We will integrate this function to one JavaScript prompt. Here we will ask the user to enter a number. The value entered by user we will check by isNan function and display message accordingly. Here is the code.
var my_string = prompt("Please enter a number","");
document.write(my_string)
if(isNaN(my_string)){
document.write ("this is not a number ");
}else{document.write ("this is a number ");
}
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| | Me2 | 07-03-2009 |
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| Cool | | tcx | 11-10-2009 |
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yes, agree,
this is very useful topic it helps me in project,
good concept not finding in other sites | | Dhaval Shingala | 25-02-2010 |
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The simplest Way is Why u check entered input is Number or not
just check on Keypress Event is number or not
The Function for checking Is number is
function isNumberKey(B,C){if(!C){C=0}var A=(B.which)?B.which:event.keyCode;if(A>31 | | Rakesh Joshi | 16-04-2010 |
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| I observed that isNaN has a flaw. If we enter a value with alphabets at the start, it will detect. But if it starts with a number and continues with alphabets or ends with alphabets, then isNaN will return false, meaning to say it is a number, which is not the desired output. Is there any other alternative? | | Adamu sani yahaya | 01-06-2010 |
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| write a javascript code that will pop-up when an input of not a number is enter and return true when number data is enter. but without using in inbuild function such as isNan. |
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