JavaScript变量少于4个字符

Question

I have "name" JavaScript variable. If variable "name" contains less than 4 characters I want to execute line: msg('name','Your name must contain minimum 4 characters.')'; I have tried something like this but it interpretated mathematical. Any idea? Thank you.

if(name < 4 ) {
  msg('name','Your name must contain minimum 4 characters.');
  return false;
}

Answer 1

if (name.length < 4) {
   ...
}

Answer 2

You probably want to check the length of the string, not the numeric value of the string itself:

if(name.length < 4) {
    // ...

Answer 3

if(name.length < 4) {
    //Do something
}

You have to check the length of the variable.

• length can also be used to check the length of an Array
• \\n (new line) is also counted as a character.

Answer 4

Depending on your definition of “character”, all answers posted so far are incorrect. The string.length answer is only reliable when you're certain that only BMP Unicode symbols will be entered. For example, 'a'.length == 1 , as you'd expect.

However, for supplementary (non-BMP) symbols, things are a bit different. For example, '𝌆'.length == 2 , even though there's only one Unicode symbol there. This is because JavaScript exposes UCS-2 code units as “characters” .

Luckily, it's still possible to count the number of Unicode symbols in a JavaScript string through some hackery. You could use Punycode.js 's utility functions to convert between UCS-2 strings and UTF-16 code points for this:

// `String.length` replacement that only counts full Unicode characters
punycode.ucs2.decode('a').length; // 1
punycode.ucs2.decode('𝌆').length; // 1 (note that `'𝌆'.length == 2`!)