What command can I use to know if a string contains only numbers?
For example, I'm using prompt :
var quantidade=prompt('Quantidade de entrada de produtos(somente números)');
I would like to check if actually in the variable quantidade has only numbers, after all we can not trust these users is not rs.
function isNumber(n) {
return !isNaN(parseFloat(n)) && isFinite(n);
}
isNumber('123'); // true
isNumber('asda123'); // false
$.isNumeric('123'); // true
$.isNumeric('asdasd123'); // false
As a curiosity, here's the implementation of isNumeric in jQuery 1.11.0:
isNumeric: function( obj ) {
// parseFloat NaNs numeric-cast false positives (null|true|false|"")
// ...but misinterprets leading-number strings, particularly hex literals ("0x...")
// subtraction forces infinities to NaN
return obj - parseFloat( obj ) >= 0;
}
Use isNaN to know if the string contains only numbers, if false it means a number:
if(!isNaN(num)) alert("a variavel num é numérica");
isNaN(123) // false, então é numerico
isNaN('123') // false então só contém numeros
isNaN('teste') // verdadeiro, não contém números
isNaN('999teste') // vardadeiro, contém números e letras
See if this helps:
function isNumeric(str) {
var er = /^[0-9]+$/;
return (er.test(str));
}
You can test the String with a regular expression:
/^\d+$/.test('0'); // Retorna true.
Being '0' is the number received in the String.
If you want to accept broken numbers, it might look like this:
/^\d+(?:\.\d+)?$/.test('0.1'); // Retorna true.
You can also create a function to reuse like this:
var
isNumeric = function(value) {
return /^\d+(?:\.\d+)?$/.test(value);
};
String.prototype.isNumeric = function() {
return isNumeric(this);
};
So you can use it in two ways:
isNumeric('0'); // Retorna true.
E:
'0.1'.isNumeric(); // Retorna true.
With jQuery already exiate a function ( jQuery.fn.isNumeric ):
$.isNumeric('0');