Does anyone know how can I check whether a variable is a number or a string in JavaScript?
If you're dealing with literal notation, and not constructors, you can use typeof:.
typeof "Hello World"; // string
typeof 123; // number
If you're creating numbers and strings via a constructor, such as var foo = new String("foo"), you should keep in mind that typeof may return object for foo.
Perhaps a more foolproof method of checking the type would be to utilize the method found in underscore.js (annotated source can be found here),
var toString = Object.prototype.toString;
_.isString = function (obj) {
return toString.call(obj) == '[object String]';
}
This returns a boolean true for the following:
_.isString("Jonathan"); // true
_.isString(new String("Jonathan")); // true