haffman code

function node(inp_name, inp_fr, inp_used, inp_code, inp_link){
    this.name = inp_name;
    this.fr = inp_fr;
    this.used = inp_used;
    this.code = inp_code;
    this.link = inp_link;
}


function reverseString(str) {
    return str.split("").reverse().join("");
}

str = 'abrakadabra';
alph = new Array();

for(i=0;i<str.length;i++){
    if (!alph[str.charAt(i)]) alph[str.charAt(i)] = 0;
    alph[str.charAt(i)]++;
}

// for(i in alph){
//     console.log(i,' ',alph[i]);
// }

tree = new Array();
var freeIdx = 0;

for(i in alph){
    n = new node(i, alph[i], 0, '', null);
    tree.push(n);
    ++freeIdx;
}


// for(i=0;i<tree.length;i++)
//     console.log(tree[i]);

var active = 1e9;
for (;active>1;){

    active = 0;
    var firstMin = freeIdx;
    var firstMinVal = 0;

    var secondMin = freeIdx;
    var secondMinVal = 0;

    for (let i = freeIdx - 1; i >= 0; --i){
        if (tree[i].used == 0){
            if (tree[i].fr < secondMinVal || secondMinVal == 0){
                if (tree[i].fr < firstMinVal || firstMinVal == 0){
                    secondMin = firstMin;
                    secondMinVal = firstMinVal;

                    firstMinVal = tree[i].fr;
                    firstMin = i;
                } else {
                    secondMin = i;
                    secondMinVal = tree[i].fr;
                }
            }
            ++active;
        }
    }
    console.log(firstMin, secondMin, active);

    if (active == 1)
        break;

    tree[freeIdx] = new node(tree[firstMin].name.concat(tree[secondMin].name),
        tree[firstMin].fr + tree[secondMin].fr,
        0, '', freeIdx);

    tree[firstMin].used = 1;
    tree[firstMin].code = '0';
    tree[firstMin].link = freeIdx;

    tree[secondMin].used = 1;
    tree[secondMin].code = '1';
    tree[secondMin].link = freeIdx;

    ++freeIdx;
}
for (let i = 0; tree[i].name.length == 1; ++i){
    var curr = i;
    var code = "";
    while(tree[curr].used == 1){
        code = code.concat(tree[curr].code);
        curr = tree[curr].link;
    }
    console.log(tree[i].name + ' ' + reverseString(code));
}