AoC 2021 day 18 Node.js

var fs = require("fs");
const internal = require("stream");

var fileName =__filename.slice(__dirname.length + 1, -3)+ ".txt";

let input = fs.readFileSync(fileName, 'utf8').toString();
let data = input.split('\n').map(s => s.split(',').join("").trim());

data = data.map(s => {
    return s.split('').map(s =>isNaN(s)?s:Number(s));
});

function add(a,b){
    let c =  ["[",...a,...b,"]"];
    while(explode(c) || split(c));
    return c;
}

function explode(a){
    let open = 0;
    for (let i = 0; i < a.length; i++) {
        const e = a[i];
        if(e == "[")open++;
        if(e == "]")open--;
        if(open == 5){
            let buf = a.splice(i, 4);
            let up=i-1;
            let down=i;
            while(down--){
                if(!isNaN(a[down])){
                    a[down]+= buf[1];
                    break;
                }
            }
            while(up++<a.length){
                if(!isNaN(a[up])){
                    a[up]+= buf[2];
                    break;
                }
            }
            a.splice(i, 0,0);
            explode(a);
            return true;
        }
    }
    return false;
}

function split(a){
    for (let i = 0; i < a.length; i++) {
        const e = a[i];
        if(!isNaN(e) && e>9){
            let l = Math.floor(e/2);
            let h = Math.ceil(e/2);
            let s = ['[',l,h,']'];
            a.splice(i,1,...s);
            return true;
        }
    }
    return false;
}

function magnitude (a){
    for (let i = 0; i < a.length; i++) {
        const e = a[i];
        if(e == "]"){
            let buf = a.splice(i-3, 4);
            let sum = buf[1]*3 + buf[2]*2;
            a.splice(i-3,0,sum);
            i-=3;
        }
    }
    return a;
}

let sum =  data[0];
for (let i = 0; i < data.length-1; i++) {
    sum = add(sum,data[i+1]);
}
let mag = magnitude(sum);
console.log(1,mag[0]);

let max = 0;
for (let i = 0; i < data.length-1; i++) {
    for (let j = 0; j < data.length; j++) {
        if(i != j){
            max = Math.max( max, magnitude( add(data[i],data[j])));
            max = Math.max( max, magnitude( add(data[j],data[i])))
        }
    }
}
console.log(2,max);