javascript-原型内部未定义

Question

I have this constructor:

var Song = function(side, name, index, duration, author, lyrics) {
    this.side = side;
    this.name = name;
    this.index = index;
    this.duration = duration;
    this.author = author;
    this.lyrics = lyrics;
    globalLyrics.push(this.lyrics);
};

and then I've created 24 instances, up to:

var song24 = new Song('Lab', 'Buffalo', 23, '3:10', 'Band', 
    ["this", "tambourine", "is", "waging", "a", "war", "will",
    "drenched", "in", "blood", "flood", "egg", "shape",
    "shaped", "rock", "rocking", "to", "kill", "the", "bull",
    "slay", "slain", "by", "dogs", "snakes", "raven", "scorpio",
    "lion", "headed", "head", "god", "rise"]);

I want to intersect user inputs, like...

 var input = ["tambourine", "this"];

...with the lyrics database; for that purpose I have an intersection function...

function setIntersection(a, b) {

    var result = [];

    for (var i = 0; i < a.length; i++) {
        if (b.indexOf(a[i]) !== -1 && result.indexOf(a[i]) === -1) {
            result.push(a[i]);
        }
    }

    return result;
}

...and a prototype function :

Song.prototype.songIntersect = function(input) {

    var bestSong = null;
    var bestCount = -Infinity;

    for (var i = 1; i <= 24; i++) {

        var currentSong = ['song' + i];
        var currentCount = setIntersection(song[i].lyrics, input).length;

        if (currentCount > bestCount) {
            bestSong = currentSong;
            bestCount = currentCount;
        }
    }

    return bestSong.name;
}       

but I get "song not defined". the error must be in the prototype function . what am I missing here? thank you.

Answer 1

You're creating 24 songs with variable names song1 , song2 , etc. However, later when you're trying to access them, you're looking for a song using a non-existent array named song . You could fix this by defining an array of songs first. This also means you don't need to know exactly how many songs there are in the code. You could dynamically add or remove songs based on an external source such as a database, public API, or user input.

var songs = [];

// add your songs like this
songs.push(new Song(/* ... */));

Also, your currentSong variable is an array containing a string of the name of the song variable. If you store the songs in an array, you could just store the index or the actual song instead.

Song.prototype.songIntersect = function(input) {
    var bestSong = null;
    var bestCount = -Infinity;

    for (var i in songs) {
        var currentCount = setIntersection(songs[i].lyrics, input).length;

        if (currentCount > best.count) {
            bestSong = song[i];
            bestCount = currentCount;
        }
    }

    return bestSong && bestSong.name;
}