how to get the substring of a string in javascript code example

Example 1: js substring

// the substring method returns a string out of another string

const str = 'Mozilla';

console.log(str.substring(1, 3));
// expected output: "oz"

console.log(str.substring(2));
// expected output: "zilla"

Example 2: substring javascript

var str = "Hello world!";
var res = str.substring(1, 4); //ell

Example 3: str.substring if 2 letters

public String firstTwo(String str) {
    return str.length() < 2 ? str : str.substring(0, 2);
}