javascript - Convert array to string while preserving brackets

Use JSON.stringify():

var x = document.getElementById("result");
x.textContent = JSON.stringify( myArray );

You can either use JSON.stringify or custom joining like this

console.log("[[" + myArray.join("],[") + "]]");
# [[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]]
console.log(JSON.stringify(myArray));
# [[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]]