Trying to pass an array to javascript from rails

Question

I am trying to pass an array back from a helper, and while it works for some part of my javascript, it doesn't work for the other half. For example, here's my helper:

def quick_stats_bar_chart
    names = []
    emails = []
    students = []
    results = []

    @exams.each do |exam|
        names << trim_exam_name(exam.name)
        emails << exam.exam_results
        student << exam.exam_results
        results << exam.exam_results
    end
    return [names, emails, students, results]
end

and here's my view in the javascript

<script>
    $(function(){
        var barData = {
            labels: ["Random"],
            datasets: [
            {
                label: "Emails",
                backgroundColor: '#dedede',
                pointBorderColor: "#dedede",
                data: <%= quick_stats_bar_chart[1] %>
            },
            {
                label: "Students",
                backgroundColor: '#a3e1d4',
                pointBackgroundColor: "#a3e1d4",
                pointBorderColor: "#a3e1d4",
                data: <%= quick_stats_bar_chart[2] %>
            },
            {
                label: "Results",
                backgroundColor: '#b5b8cf',
                pointBackgroundColor: "#b5b8cf",
                pointBorderColor: "#b5b8cf",
                data: <%= quick_stats_bar_chart[3] %>
            }
            ]
        };

        var barOptions = {
            responsive: true
        };


        var ctx2 = document.getElementById("participationChart1").getContext("2d");
        new Chart(ctx2, {type: 'bar', data: barData, options:barOptions});
    });

The code labels: ["Random"] is where I have issues. If I leave it like this, it works, but I cannot use <%= quick_stats_bar_chart[0] %> because I get an error stating

SyntaxError: expected expression, got '&'

The labels option is supposed to take an array, so I'm not sure why the array isn't being passed and parsed correctly.

Any thoughts? Again, I can manually put in an array, but trying to call it from the helper gives me this error.

Edit

Here's what quick_stats_bar_chart[0] looks like:

[2] pry(#<#<Class:0x00007f0c99675370>>)> quick_stats_bar_chart[0]
=> ["Random.."]
[3] pry(#<#<Class:0x00007f0c99675370>>)> quick_stats_bar_chart[1]
=> [1]

It gives me an error on [0] but not [1].

Here's the FULL variable output:

[1] pry(#<#<Class:0x00007f0c99675370>>)> quick_stats_bar_chart
=> [["Random.."], [1], [1], [0]]

Here's with raw [2] pry(#<#>)> raw(quick_stats_bar_chart[0]) => "[\"Random..\"]"

Have you tried to debug what is inside quick_stats_bar_chart ? — Roman Kiselenko
– Roman Kiselenko, Commented Sep 19, 2018 at 6:06
Yep, When I place a binding.pry and look at quick_stats_bar_chart[0], it's an array, just like the one I provided manually and everything worked (manually that is) — LewlSauce
– LewlSauce, Commented Sep 19, 2018 at 6:07
Looks like it's not valid array for javascript code. Show what is inside that variable. — Roman Kiselenko
– Roman Kiselenko, Commented Sep 19, 2018 at 6:08
What's strange though is that the other ones are arrays too and they're being accepted just fine, except quick_stats_bar_chart[1], [2], and [3] are actually array containing integers, unlike [0] which is a string. — LewlSauce
– LewlSauce, Commented Sep 19, 2018 at 6:08
Your errors is clear, it's syntax error, so your array isnt valid. — Roman Kiselenko
– Roman Kiselenko, Commented Sep 19, 2018 at 6:09

Roman Kiselenko · Accepted Answer · 2018-09-19 06:25:00Z

1

You need marks a string as trusted safe. It will be inserted into HTML with no additional escaping performed. Use the raw() method for his.

answered Sep 19, 2018 at 6:25

Roman Kiselenko

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