inconsistent behaviour of javascript (particlesJS)
Question
I am trying to make a login page with work. Below is the body of main html page (only body is shown to keep things concise):
<body>
<div class="container">
<div id="login-box">
<div class="controls">
<input type="text" name="username" placeholder="Username" class="form-control" />
<input type="text" name="username" placeholder="Password" class="form-control" />
<button type="button" class="btn btn-default btn-block btn-custom">Login</button>
</div> <!-- /.controls -->
</div> <!-- /#login-box -->
</div> <!-- /.container -->
<div id="particles-js"></div>
<script src="https://cdn.jsdelivr.net/particles.js/2.0.0/particles.min.js"> </script>
<script>
particlesJS.load('particles-js', 'particles.json', function() {
console.log('callback - particles.js config loaded');
});
</script>
</body>
In addition to this I have a css and particles.json static files.
Everything works when I execute it on a web browser with apache2 as web server.
Then I take the exact same files and use it in a Golang program:
func main(){
templates := template.Must(template.ParseFiles("../../templates/index.html"))
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request){
if err:= templates.ExecuteTemplate(w, "index.html", nil) ; err != nil{
http.Error(w, err.Error(), http.StatusInternalServerError)
}
//fmt.Fprintf(w, "Welcome to Gopherland")
})
http.Handle("/css/", http.FileServer(http.Dir("style")))
http.Handle("/js/", http.FileServer(http.Dir("style")))
http.ListenAndServe(":5000", nil)
}
and it fails to parse particles.json file:
SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
No other compile time or run time error is thrown by Go. This error appears in browser console. I have checked the validity of particles.json file.
Can someone help please?
Contents of particles.json:
{
"particles": {
"number": {
"value": 80,
"density": {
"enable": true,
"value_area": 800
}
},
"color": {
"value": "#ffffff"
},
"shape": {
"type": "circle",
"stroke": {
"width": 0,
"color": "#000000"
},
"polygon": {
"nb_sides": 5
},
"image": {
"width": 100,
"height": 100
}
},
"opacity": {
"value": 0.5,
"random": false,
"anim": {
"enable": false,
"speed": 1,
"opacity_min": 0.1,
"sync": false
}
},
"size": {
"value": 5,
"random": true,
"anim": {
"enable": false,
"speed": 40,
"size_min": 0.1,
"sync": false
}
},
"line_linked": {
"enable": true,
"distance": 150,
"color": "#ffffff",
"opacity": 0.4,
"width": 1
},
"move": {
"enable": true,
"speed": 6,
"direction": "none",
"random": false,
"straight": false,
"out_mode": "out",
"attract": {
"enable": false,
"rotateX": 600,
"rotateY": 1200
}
}
},
"interactivity": {
"detect_on": "canvas",
"events": {
"onhover": {
"enable": true,
"mode": "repulse"
},
"onclick": {
"enable": true,
"mode": "push"
},
"resize": true
},
"modes": {
"grab": {
"distance": 400,
"line_linked": {
"opacity": 1
}
},
"bubble": {
"distance": 400,
"size": 40,
"duration": 2,
"opacity": 8,
"speed": 3
},
"repulse": {
"distance": 200
},
"push": {
"particles_nb": 4
},
"remove": {
"particles_nb": 2
}
}
},
"retina_detect": true,
"config_demo": {
"hide_card": false,
"background_color": "#b61924",
"background_image": "",
"background_position": "50% 50%",
"background_repeat": "no-repeat",
"background_size": "cover"
}
}
2 answers
solution1
2 2018-05-14 23:32:00
http.HandleFunc("/", is matching anything that doesn't match elsewhere, it's essentially a catch all as the ServeMux documentation states:
Patterns name fixed, rooted paths, like "/favicon.ico", or rooted subtrees, like "/images/" (note the trailing slash). Longer patterns take precedence over shorter ones, so that if there are handlers registered for both "/images/" and "/images/thumbnails/", the latter handler will be called for paths beginning "/images/thumbnails/" and the former will receive requests for any other paths in the "/images/" subtree.
Since it is trying to load particles.json , and there is no better match, it is loading your index page.
You need to add another route, something like:
http.HandleFunc("/particles.json", func(w http.ResponseWriter, r *http.Request) {
http.ServeFile(w, r, "./path/to/particles.json")
})
solution2
0 2018-05-21 13:35:01
Thanks for your invaluable comments. I did try every options suggested above but couldn't make the program to work until I figured out that I had a silly misconception (due to lack of knowledge of course) that " / " in: *http.HandleFunc(" / ", func(w http.ResponseWriter, r http.Request) is the root of my project folder ie the folder under which I had my ./src, ./bin, ./style/css/ and ./style/js/
However, that wasn't the case. I modified the code to this:
func main () {
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request){
http.ServeFile(w, r, r.URL.Path)
})
http.ListenAndServe(":5000" , nil)
}
compiled and ran. Only to find that if I don't pass any path it was listing the "root" filesystem's contents like, /bin, /home. This was enough for me to understand that Go code is considering "/" filesystem's root and NOT project's root folder. I then updated absolute path of css and json file in my index.html and boom... It worked!
Thanks again for your help. It did help me a lot.
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