Hello fellow JavaScript developers!
I’m working with variables and need a quick refresher on proper type checking.
For example, given var a_string = "Hello, I'm a string.";, what’s the correct way to test if a_string is indeed a string? I tried using if (a_string typeof 'string'), but it doesn’t work.
What’s the proper syntax to check if string type a variable is in JavaScript?
Thanks in advance for the help!
Hii! What you are going through @archna.vv is a common initial stumble!
The easiest and most common way to do this is simply by using the typeof operator. You just write:
if (typeof a_string === 'string') {
// it's a string!
}
Make sure you include the triple equals === for strict comparison, and remember that typeof goes before the variable name.
Hope this clears up the confusion and helps you with your type checks!
Hi! Adding another layer to the discussion on accurately checking if a variable is a string, building on the typeof method suggested by @emma-crepeau.
@archna.vv If you want to be extra sure, especially if you might encounter actual String objects (like those created with new String()), you can also combine typeof with instanceof:
if (typeof a_string === 'string' || a_string instanceof String) {
// yep, it's a string or String object
}
This comprehensive check covers both primitive strings (like "hello") and String wrapper objects, ensuring your logic handles all possible string-like values.
Thanks
Hi @archna.vv!!!
Sometimes people use **Object.prototype.toString.call()** to check types in a more robust way, especially for very specific scenarios:
if (Object.prototype.toString.call(a_string) === '[object String]') {
// definitely a string
}
This method can be particularly handy if you want to explicitly avoid tricky edge cases where typeof or instanceof might not give the full picture for built-in objects. However, for most common uses, typeof is often sufficient.
I assure you, this addition to your JavaScript toolbox would be helpful. Thank you