Variable substitution not working in $in in mongo with node js

Question

I have constructed the node path as /57639afa5961debc1b256745/, /5763c5d17d05688c1838c7a3/, but when I try to subtitute with nodepath it gets the result as empty array even though it has the children:

Degree.prototype.findByPath = function(dbObj, degrees) {
    var nodePath = '';

    for(var i in degrees) {
        nodePath = nodePath + '/' + degrees[i]['_id'] + '/, ';
    }

    return new Promise(function (resolve, reject) {
        console.log(nodePath);
        dbObj.collection('degree').find({ 
            'path': {
                '$in': 
                    [ nodePath ] 
                } 
            }).toArray((err, results) => {
                if(err) {
                    reject(err);
                } else {
                    var nodes;

                    if(results != null)
                        nodes = degrees.concat(results);
                    else
                        nodes = degrees;

                    resolve(nodes);
                }               
            });
    }); 
};

JohnnyHK · Accepted Answer · 2016-06-20 12:11:43Z

1

You need to build up nodePath as an array of strings rather than one comma-separated string. And if you want the id values treated as regular expressions, use the RegExp constructor instead of adding slash characters:

var nodePath = [];

for(var i in degrees) {
    nodePath.push(new RegExp(degrees[i]['_id']));
}

return new Promise(function (resolve, reject) {
    console.log(nodePath);
    dbObj.collection('degree').find({ 
        'path': {
            '$in': nodePath
            } 
        }).toArray((err, results) => {...

edited Jun 20, 2016 at 12:11

answered Jun 17, 2016 at 13:49

JohnnyHK

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3 Comments

Sethu Over a year ago

Degree.prototype.findByPath = function(dbObj, degrees) { var nodePath = ''; for(var i in degrees) { nodePath = nodePath + degrees[i]['_id'] + ', '; } if(nodePath != '') nodePath = '[' +nodePath + ']'; return new Promise(function (resolve, reject) { console.log(nodePath); dbObj.collection('degree').find({ 'path': { '$regex': nodePath } }).toArray((err, results) => {

JohnnyHK Over a year ago

@Sethu Sorry, I don't understand your comment.

Sethu Over a year ago

your code not worked as expected. So i try with $regex it works as expected.

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