how to join two element in array in javascript code example

Example 1: .join in javascript

const elements = ['Sun', 'Earth', 'Moon'];

console.log(elements.join());
// output: "Sun,Earth,Moon"

console.log(elements.join(''));
// output: "SunEarthMoon"

console.log(elements.join('-'));
// output: "Sun-Earth-Moon"

Example 2: javascript concat two arrays

//ES6
const array3 = [...array1, ...array2];