decipher.js

/* Code to run in the browser console of `go/techcon-lightningtalks` */

let loadData = function() {
    // Array holding the data
    let data = Array();
    // Keep track of `H2` elements
    let index = 1;

    // Keep track of pillars
    let pillar = 1;
    // Make sure not to overflow the `H2` elements
    let length = document.getElementsByTagName("h2").length;
  
    // Loop over pillars
    while(document.getElementsByTagName("h2")[index].innerText.startsWith(pillar)) {
        // Create a new pillar array entry, index 1
        data[pillar] = Array();
        // Keep track of topics
        let topic = 1;
        // Scan element and all its siblings for a given pillar
        let elem;
        while(elem = document.getElementsByTagName("h2")[++index].nextElementSibling) {
            // Create a new topic array entry, index 1
            data[pillar][topic] = Array();
            // Keep track of talks
            let talk = 1;
            // Scan text under a talk
            while(elem && elem.innerText.startsWith(talk)) {
                // Create a new talk entry, this is the actual data we are looking for
                // We care about title and text body only
                // Thus skipping the second element sibling
                // Assume that always a talk has 3 sibling lines
                data[pillar][topic][talk] = Array();
                // Line 0
                data[pillar][topic][talk][0] = elem.innerText.substr(3);
                // Line 2 (mapped into 1 to match the cipher)
                elem = elem.nextElementSibling.nextElementSibling;
                data[pillar][topic][talk][1] = elem.innerText;
              
                // Move to next talk
                elem = elem.nextElementSibling;
                talk++;
            }
            // Move to next topic
            topic++;
          
            // Make sure not to overflow the `H2` index
            if(length-index==1) {
                break;
            }
        }
        // Move to next pillar
        pillar++;
    }

    return data;
}

let decipher = function(cipher) {
    // FIXME: Can load the data once per page instead of multiple times per operation
    let data = loadData();
    let s ="";
    for(let i=0; i<cipher.length; i++) {
        let x = cipher[i].split(":");
        // Rearrange the cipher elements into correct order
        // And then extract char from `data` array
        s += data[x[0]][x[1]][x[3]][x[2]].charAt(x[4]-1);
    }

    return s;
}

/* === end of code === */

/* Decipher any text, example usage: */

console.log(
    "Solution is:\n",
    decipher(
        ['6:1:1:3:44', '9:2:0:2:105', '1:2:1:3:353', '5:5:1:2:75', '1:5:1:3:165', '5:4:1:1:129', '5:3:0:4:74', '1:5:0:3:22', '1:5:1:3:212', '4:1:1:4:217', '2:5:1:1:64', '2:2:1:2:125', '1:4:1:2:206', '7:2:1:2:27', '5:5:1:1:120', '8:4:1:2:45', '5:5:0:2:69', '1:5:0:1:51', '3:5:1:2:265', '7:2:1:1:172', '7:2:0:2:5', '1:5:0:1:17', '10:1:0:1:35', '3:1:1:4:21', '1:4:1:3:80', '1:1:0:1:7', '8:4:0:1:7', '1:2:0:2:58']
    )
);