Finding The Missing Sequence Number In A File

Hi I have to find a missing number in an xml file. but I feel difficulty to find. Pls suggest some ideas. Example A file contains an tag which include id i.e page-1,2..

Solution 1:

I'll take some assumptions regarding your input. Please add validations as necessary:

var lines = ['<p>have a great <a id="page-1"/>day. How are you.</p>',
    '<p><a id="page-2"/>Have a nice day.</p>',
    '<p>How <a id="page-5"/>are you</p>',
    '<p>Life is so exciting<a id="page-6"/></p>'];

    var sequences = [];
    lines.forEach(function(line) {

        // Not efficient but simple
        // Let jQuery parse this string to object, so we won't need regexp
        var obj = $(line);

        // Assuming there's always A and ID attribute
        var id = obj.find("a").attr("id").split("-");

        // Assuming sequence is always last
        sequences.push(parseInt(id[id.length - 1]));
    });

    sequences.sort();

    // Again, inefficient, but will do the job
    var last = sequences[sequences.length - 1];

    for (var i = last; i >= 0; i--) {
        if (sequences.indexOf(i) < 0) {
            console.log(i + " is missing");
        }
    }