function isBlank(subject) {
    var subjectString = coerceToString(subject);
    return subjectString.trim().length === 0;
  }
Checks whether `subject` is empty or contains only whitespaces.

@function isBlank
@static
@since 1.0.0
@memberOf Query
@param {string} [subject=''] The string to verify.
@return {boolean} Returns `true` if `subject` is empty or contains only whitespaces or `false` otherwise.
@example
v.isBlank('');
// => true

v.isBlank('  ');
// => true

v.isBlank('World');
// => false