javascript - How to detect string which contains only spaces?

Question

A string length which contains one space is always equal to 1:

alert('My str length: ' + str.length);

The space is a character, so:

str = "   ";
alert('My str length:' + str.length); // My str length: 3

How can I make a distinction between an empty string and a string which contains only spaces? How can I detect a string which contain only spaces?

Answer 1

To achieve this you can use a Regular Expression to remove all the whitespace in the string. If the length of the resulting string is 0, then you can be sure the original only contained whitespace. Try this:

var str = "    ";
if (!str.replace(/s/g, '').length) {
  console.log('string only contains whitespace (ie. spaces, tabs or line breaks)');
}