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I am using select2 in an express app to make an input box where users can select subjects from a list, and can update this list with any newly added options.

The thing I'm struggling with is that select2 runs client-side, whereas any data I use to seed my <option> tags (that I want to append new options to) is server-side.

I want users to be able to add subjects that don't exist in the original list, so that future users will be presented with newly added options (as well as the original ones)

These are the options I've considered for achieving this (in increasing desirability):

• Add new <option>Subject</option> html tags for each added tag
• Push new tags to an array, and seed the <option>s from this array
• Seed the <option> from a json object, and update this object on tag creation
• Seed the <option> from an external database (e.g. mongoose), and update this on tag creation

As far as I can see, all of these options require that my client-side code (select2-js) talks to server-side code (where my array, .json file or mongoose schema would be), and I have no idea how to go about doing this.

In my current approach I am attempting to to specify a "local" json file as my data source in my select2 call (see here). However, this doesn't seed the database with any options, so this isn't working as I expected.

I then check if each new tag exists in an array (dataBase), and add it to the database if not:

// Data to seed initial tags:
var dataBase = [
    { id: 0, text: 'Maths'},
    { id: 1, text: 'English'},
    { id: 2, text: 'Biology'},
    { id: 3, text: 'Chemistry'},
    { id: 4, text: 'Geography'}
];


$(document).ready(function() {
    $('.select2-container').select2({
        ajax: {
            url: '../../subjects.json',
            dataType: 'json',
        },
        width: 'style',
        multiple: true,
        tags: true,
        createTag: function (tag) {
            var isNew = false;
            tag.term = tag.term.toLowerCase();
            console.log(tag.term);
            if(!search(tag.term, dataBase)){
                if(confirm("Are you sure you want to add this tag:" + tag.term)){
                    dataBase.push({id:dataBase.length+1, text: tag.term});
                    isNew = true;
                }
            }
            return {
                        id: tag.term,
                        text: tag.term,
                        isNew : isNew
                    };
        },
        tokenSeparators: [',', '.']
    })
});

// Is tag in database?
function search(nameKey, myArray){
    for (var i=0; i < myArray.length; i++) {
        if (myArray[i].text.toLowerCase() === nameKey.toLowerCase()) {
            return true
        }
    }
    return false
};

However, this approach will add the new tags to an array that is destroyed once I refresh the page, and new tags are not stored.

How can I modify this to load server-side data (json, mongoose document or anything else that is considered a best practice), and update this data with newly added options (that pass my tests)?

I am using select2 in an express app to make an input box where users can select subjects from a list, and can update this list with any newly added options.

The thing I'm struggling with is that select2 runs client-side, whereas any data I use to seed my <option> tags (that I want to append new options to) is server-side.

I want users to be able to add subjects that don't exist in the original list, so that future users will be presented with newly added options (as well as the original ones)

These are the options I've considered for achieving this (in increasing desirability):

• Add new <option>Subject</option> html tags for each added tag
• Push new tags to an array, and seed the <option>s from this array
• Seed the <option> from a json object, and update this object on tag creation
• Seed the <option> from an external database (e.g. mongoose), and update this on tag creation

As far as I can see, all of these options require that my client-side code (select2-js) talks to server-side code (where my array, .json file or mongoose schema would be), and I have no idea how to go about doing this.

In my current approach I am attempting to to specify a "local" json file as my data source in my select2 call (see here). However, this doesn't seed the database with any options, so this isn't working as I expected.

I then check if each new tag exists in an array (dataBase), and add it to the database if not:

// Data to seed initial tags:
var dataBase = [
    { id: 0, text: 'Maths'},
    { id: 1, text: 'English'},
    { id: 2, text: 'Biology'},
    { id: 3, text: 'Chemistry'},
    { id: 4, text: 'Geography'}
];


$(document).ready(function() {
    $('.select2-container').select2({
        ajax: {
            url: '../../subjects.json',
            dataType: 'json',
        },
        width: 'style',
        multiple: true,
        tags: true,
        createTag: function (tag) {
            var isNew = false;
            tag.term = tag.term.toLowerCase();
            console.log(tag.term);
            if(!search(tag.term, dataBase)){
                if(confirm("Are you sure you want to add this tag:" + tag.term)){
                    dataBase.push({id:dataBase.length+1, text: tag.term});
                    isNew = true;
                }
            }
            return {
                        id: tag.term,
                        text: tag.term,
                        isNew : isNew
                    };
        },
        tokenSeparators: [',', '.']
    })
});

// Is tag in database?
function search(nameKey, myArray){
    for (var i=0; i < myArray.length; i++) {
        if (myArray[i].text.toLowerCase() === nameKey.toLowerCase()) {
            return true
        }
    }
    return false
};

However, this approach will add the new tags to an array that is destroyed once I refresh the page, and new tags are not stored.

How can I modify this to load server-side data (json, mongoose document or anything else that is considered a best practice), and update this data with newly added options (that pass my tests)?

• javascript
• jquery
• ajax
• express
• jquery-select2

Share Improve this question Follow edited Mar 25, 2019 at 10:27 fugu asked Mar 15, 2019 at 17:41 fugufugu 6,57899 gold badges4242 silver badges7979 bronze badges 2

• 1 Use ajax to populate the json on the page. Then use the json to populate the select2 as you are currently doing. Attach the json to document.ready and to the database update to get your result – Lelio Faieta Commented Mar 18, 2019 at 11:00
• @LelioFaieta - thanks for the pointers. Any chance you could pad this out as an answer? – fugu Commented Mar 18, 2019 at 11:02

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 5 +50

On your server-side, you can have an api that maintains and returns the tag array. If you want the array to persist even after server shutdown, you can store the tags array in a database.

Server side:

let dataBase = [
{ id: 0, text: 'Maths'},
{ id: 1, text: 'English'},
{ id: 2, text: 'Biology'},
{ id: 3, text: 'Chemistry'},
{ id: 4, text: 'Geography'}
];
//Assuming you have a nodejs-express backend
app.get('/tags', (req,res) => {
res.status(200).send({tags: dataBase});
} );

Client Side:

$(document).ready(function() {
dataBase=[];
$.get("YOUR_SERVER_ADDRESS/tags", function(data, status){
console.log("Data: " + data + "\nStatus: " + status);
dataBase = data;
});

$('.select2-container').select2({
    data: dataBase,
    placeholder: 'Start typing to add subjects...',
    width: 'style',
    multiple: true,
    tags: true,
    createTag: function (tag) {
        var isNew = false;
        tag.term = tag.term.toLowerCase();
        console.log(tag.term);
        if(!search(tag.term, dataBase)){
            if(confirm("Are you sure you want to add this tag:" + tag.term)){
                dataBase.push({id:dataBase.length+1, text: tag.term});
                isNew = true;
                //Update the tags array server side through a post request
            }
        }
        return {
                    id: tag.term,
                    text: tag.term,
                    isNew : isNew
                };
    },
    tokenSeparators: [',', '.']
})
});

// Is tag in database?
function search(nameKey, myArray){
for (var i=0; i < myArray.length; i++) {
    if (myArray[i].text.toLowerCase() === nameKey.toLowerCase()) {
        return true
    }
}
return false
};

You can use select2:select and select2:unselect event for this.

var dataBase = [{
    id: 0,
    text: 'Maths'
  },
  {
    id: 1,
    text: 'English'
  },
  {
    id: 2,
    text: 'Biology'
  },
  {
    id: 3,
    text: 'Chemistry'
  },
  {
    id: 4,
    text: 'Geography'
  }
];

$(document).ready(function() {
  $('.select2-container').select2({
    data: dataBase,
    placeholder: 'Start typing to add subjects...',
    width: 'style',
    multiple: true,
    tags: true,
    createTag: function(tag) {
      return {
        id: tag.term,
        text: tag.term,
        isNew: true
      };
    },
    tokenSeparators: [',', '.']
  })
  $(document).on("select2:select select2:unselect", '.select2-container', function(e) {
    var allSelected = $('.select2-container').val();
    console.log('All selected ' + allSelected);

    var lastModified = e.params.data.id;
    console.log('Last Modified ' + lastModified);

    var dbIdArray = dataBase.map((i) => i.id.toString());
    var allTagged = $('.select2-container').val().filter((i) => !(dbIdArray.indexOf(i) > -1))
    console.log('All Tagged ' + allTagged);
  });
});

.select2-container {
  width: 200px;
}

<script src="https://cdnjs.cloudflare./ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare./ajax/libs/select2/4.0.6-rc.0/js/select2.min.js"></script>
<link href="https://cdnjs.cloudflare./ajax/libs/select2/4.0.6-rc.0/css/select2.min.css" rel="stylesheet" />

<select class="select2-container"></select>

Here's what I've ended up with (thanks to both answers):

1. Set up a Mongoose DB to hold subjects:

models/subjects.js

var mongoose = require("mongoose");

var SubjectSchema = new mongoose.Schema({
    subject: { type: String },
});

module.exports = mongoose.model("Subjects", SubjectSchema);

2. Set up api routes in node js express backend:
routes/api.js

var express    = require("express");
var router = express.Router();
var Subjects = require("../models/subjects");

// GET route for all subjects in db
router.get("/api/subjects/all", function(req, res){
    Subjects.find().lean().exec(function (err, subjects) {
        return res.send(JSON.stringify(subjects));
    })
});

// POST route for each added subject tag
router.post("/api/subjects/save", function(req, res){
    var newSubject = {};
    newSubject.subject = req.body.subject;

    console.log("Updating db with:" + newSubject);

    var query = {subject: req.body.subject};

    var options = { upsert: true, new: true, setDefaultsOnInsert: true };

    // Find the document
    Subjects.findOneAndUpdate(query, options, function(error, subject) {
        if (error) return;
        console.log("Updated db enry: " + subject);
    });

    return res.send(newSubject);
});

3. Set up select2 input field:
public/js/select2.js

var dataBase=[];
$(document).ready(function() {
    // Get all subjects from api (populated in step 2) and push to dataBase array
    $.getJSON('/api/subjects/all')
    .done(function(response) {
        $.each(response, function(i, subject){
            dataBase.push({id: subject._id, text: subject.subject});
        })
        console.log("dataBase: " + dataBase);
    })
    .fail(function(err){
        console.log("$.getJSON('/api/subjects/all') failed")
    })

    // Get data from api, and on 'selecting' a subject (.on("select2:select"), check if it's in the dataBase. If it is, or the user confirms they want to add it to the database, send it to POST route, and save it to our Subjects db.

    $('.select2-container')
    .select2({
        ajax: {
        url : "/api/subjects/all",
        dataType: 'json',
        processResults: function (data) {
            return {
                results: $.map(data, function(obj) {
                    return { id: obj._id, text: obj.subject };
                    })
                };
            }
        },
        placeholder: 'Start typing to add subjects...',
        width: 'style',
        maximumSelectionLength: 5,
        multiple: true,

        createTag: function(tag) {
            return {
                id: tag.term,
                text: tag.term.toLowerCase(),
                isNew : true
            };
        },

        tags: true,
        tokenSeparators: [',', '.']
    })
    .on("select2:select", function(e) {
        if(addSubject(dataBase, e.params.data.text)){
            console.log(e.params.data.text + " has been approved for POST");
            ajaxPost(e.params.data.text)
        } else {
            console.log(e.params.data.text + " has been rejected");
            var tags = $('#selectSubject select').val();
            var i = tags.indexOf(e.params.data.text);
            console.log("Tags: " + tags);
            if (i >= 0) {
                tags.splice(i, 1);
                console.log("post splice: " + tags);
                $('select').val(tags).trigger('change.select2');
            }
        }
    })

    function ajaxPost(subject){
        console.log("In ajaxPost");
        var formData = {subject : subject}
        $.ajax({
            type : "POST",
            contentType : "application/json",
            url : "/api/subjects/save",
            data : JSON.stringify(formData),
            dataType : 'json'})
            .done(console.log("Done posting " + JSON.stringify(formData)))
            .fail(function(e) {
                alert("Error!")
                console.log("ERROR: ", e);
            });
    }

    function addSubject(subjects, input) {
        if (!input || input.length < 3) return false

        var allSubjects = [];

        $.each(subjects, function(i, subject){
            if(subject.text) allSubjects.push(subject.text.toLowerCase())
        });

        console.log("Here is the entered subject: " + input);

        if(allSubjects.includes(input)){
            console.log(input + " already exists")
            return true
        }

        if(confirm("Are you sure you want to add this new subject " + input + "?")){
            console.log(input + " is going to be added to the database");
            return true
        } 
        console.log(input + " will NOT to added to the database");
        return false
    }

});

This works, but I would love to hear feedback on this approach!

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