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. Here’s a working example:

const isWhitespaceString = str => !str.replace(/\s/g, '').length

console.log('isWhitespaceString str1:', isWhitespaceString('  w ')); // false
console.log('isWhitespaceString str2:', isWhitespaceString('    ')); // true
console.log('isWhitespaceString str3:', isWhitespaceString('')); // true