two words first letter in javascript code example

Example 1: js get words first letter

var str = "Java Script Object Notation";
var matches = str.match(/\b(\w)/g); // ['J','S','O','N']
var acronym = matches.join(''); // JSON

console.log(acronym)

Example 2: get first two letter of an array javascript

var str = '012123';
var strFirstThree = str.substring(0,3);

console.log(str); //shows '012123'
console.log(strFirstThree); // shows '012'