The length property represents the length of a string.
str.lengthThis property returns the number of code units in the string. , the string format used by JavaScript, uses a single 16-bit code unit to represent the most common characters, but needs to use two code units for less commonly-used characters, so it's possible for the value returned by length to not match the actual number of characters in the string.
For an empty string, length is 0.
The static property String.length returns the value 1.
var x = 'Mozilla';
var empty = '';
console.log('Mozilla is ' + x.length + ' code units long');
/* "Mozilla is 7 code units long" */
console.log('The empty string has a length of ' + empty.length);
/* "The empty string has a length of 0" */
Created by Mozilla Contributors and licensed under CC-BY-SA 2.5