Apply function to field on all documents returned from MongoDB query in nodejs

Question

Apply function to field on all documents returned from MongoDB query in nodejs

I want to apply a truncate(string, words) function to the 'body' field of all Article documents returned by a mongoose query. An example would be as follows:

Article.find({})
    .sort({'meta.created': 'desc'})
    .limit(6)
    .exec(function(err, articles) {
                // Truncate the article.body field on each articles here?
        res.render(articles: articles});
    });

With a simple truncate function something like:

function truncate(string, words) {
    var value_arr = string.split( ' ' );
    if( words < value_arr.length ) {
        value = value_arr.slice(0, words).join( ' ' );
    }
    return value;
}

How can I apply this function to each articles body field (retaining the articles structure for use in a template)? Thanks in advance.

node.js
mongodb
mongoose

Answer 1

The proper way, I believe, would be to add a truncatedBody property to your Article, and implement the truncate method as a static:

Article.methods.setTruncatedBody = function(limit){
    //If truncatedBody is already computed, don't do anything
    if(this.truncatedBody) 
        return;

    var value_arr = body.split( ' ' );
    if( limit < value_arr.length ) {
        this.truncatedBody = value_arr.slice(0, words).join( ' ' );
    }
    else
        this.truncatedBody = body;
}

Then, in your controller:

Article.find({})
    .sort({'meta.created': 'desc'})
    .limit(6)
    .exec(function(err, articles) {
        for(var article in articles)
            article.setTruncatedBody(5);
        res.render(articles: articles});
    });