How Can You Determine if a JavaScript Variable Holds a Number or a String?

Identifying the Nature of Variables in JavaScript: Number or String

Determining whether a variable holds a number or a string value is essential for effective data manipulation in JavaScript. Here's an exploration of the methods available to make this type verification:

Using typeof:

The operator typeof returns the type of a variable as a string:

typeof "Hello World"; // "string"
typeof 123;           // "number"

Handling Constructor-Created Variables:

Keep in mind that constructor-created variables (e.g., var foo = new String("foo")) may return "object" as their type even though they contain string values.

Leveraging Underscore.js:

For a more robust approach, consider utilizing the following method from Underscore.js:

var toString = Object.prototype.toString;

_.isString = function (obj) {
  return toString.call(obj) == '[object String]';
}

This method returns true for the following:

_.isString("Jonathan"); // true
_.isString(new String("Jonathan")); // true

By understanding these methods, you can reliably identify variable types, ensuring efficient code execution and data integrity.

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