无法弄清楚为什么我的对象中的值正在发生变化

Question

I'm trying to figure out why the values in my chart are not coming out correctly. When I log the values of learningLanguages[j].count++ as it is looping they are accurate. However, when I log n in the map function in the chart $.map(nativeLanguages, function(n) {...}) , the counts are all incorrect (and seemingly arbitrary)

var getLanguages = $.get('/languages.json', function(languages){
        // top level language arrays
        learningLanguages = []
        nativeLanguages = []

        // object constructor that correctly formats the language objects
        function Language(lang) {
            this.language = lang;
            this.count = 0;
        }

        // Loop through the languages, create an object for each, push to top level language arrays
        for(i = 0; i < languages.length; i++) {
            currentLanguage = new Language(languages[i].language)

            learningLanguages.push(currentLanguage)
            nativeLanguages.push(currentLanguage)
        }
     });

    // once the languages call is complete find signed-in user's info
    getLanguages.done(function() {
        $.get('/users.json', function(response) {
            // console.log(response)
            // adds the total number of users to the DOM
            var numberOfUsers = response.length
            $('#userCount').append('<h1>Total Users: ' + numberOfUsers + '</h1>')
            // find the number of approved users
            // var numberApproved = 0
            // for (i = 0; i < response.length; i++) {
            //     if (response[i].approved === true) {
            //         numberApproved++
            //     }
            // }
            // Add the number of approved users to the DOM
            // $('#userCount').append('<h1>Total Approved Users: ' + numberApproved + '</h1>')


            // search for the language in the array and increase the count for that language
            for (i = 0; i < response.length; i++) {
                var userLearningLanguage = response[i].learning_language

                for (j = 0; j < learningLanguages.length; j++) {
                    if (learningLanguages[j].language === userLearningLanguage) {
                        learningLanguages[j].count++
                    }
                }
            }
            // search for the language in the array and increase the count for that language
            for (i = 0; i < response.length; i++) {
                var userNativeLanguage = response[i].native_language
                for (j = 0; j < nativeLanguages.length; j++) {
                    if (nativeLanguages[j].language === userNativeLanguage) {
                        nativeLanguages[j].count++
                    }
                }
            }

            var ctx = $("#languageComparisonChart");
            var myChart = new Chart(ctx, {
                type: 'bar',
                data: {
                    labels: 
                        $.map(learningLanguages, function(n) {
                            return n.language
                        }),
                    datasets: [{
                        label: '# of Learners',
                        data:  $.map(learningLanguages, function(n) {
                                return n.count
                            }),
                        backgroundColor: 'rgba(255, 99, 132, 0.2)',
                        borderColor: 'rgba(255,99,132,1)',
                        borderWidth: 1
                    },
                    {
                        label: '# of Native Speakers',
                        data:  $.map(nativeLanguages, function(n) {
                            console.log(n)
                                return n.count
                            }),
                        backgroundColor: 'rgba(54, 162, 235, 0.2)',
                        borderColor: 'rgba(54, 162, 235, 1)',
                        borderWidth: 1
                    }]
                },
                options: {
                    scales: {
                        yAxes: [{
                            ticks: {
                                beginAtZero:true
                            }
                        }]
                    },
                    responsive: false,
                    maintainAspectRatio: true
                }
            });
        })
    });
}   

Answer 1

Part of your problem stems from pushing the same object into the 2 different arrays here:

    for(i = 0; i < languages.length; i++) {
        currentLanguage = new Language(languages[i].language)

        learningLanguages.push(currentLanguage)
        nativeLanguages.push(currentLanguage)
   }

This does not copy currentLanguage into each, it pushes references of the same object into each.

Then whatever you do to that object reference in one will be reflected in the other

Try making 2 separate objects

    for(i = 0; i < languages.length; i++) { 
        learningLanguages.push(new Language(languages[i].language))
        nativeLanguages.push(new Language(languages[i].language))
   }

the use of global variables will also get you into trouble...don't do it!

Answer 2

learningLanguages = []
nativeLanguages = []

These two variables look like they are not defined in an above scope - thus the second XHR call does not know about these variables.

Second piece of the answer is reference to the same object instance, with the same "count" attribute touched twice.

I'd suggest two options are here:

• use new Language(...) for each of these two arrays separately
• or have a separate counter for each type of native/learning counts.