javascript - If input has spaces only

Hi there everyone how can I detect if the user input has just empty spaces?

Detect this:

input = ' ';

input = '          ';
etc...

DO NOT detect this:

input 'hi there';

I just want to detect if there is a space in the input and that's it?

---

Here is what i have tried:

function whitespaceDetect(s) {
  return /\s/g.test(s);
}

if(whitespaceDetect(document.getElementById("name").value)) {

    alert('error!');
}

but this comes up with an error if the name is "john doe";

What way is the fastest to process? How can i achieve this with or without jquery?