Sorona Sorona - 4 months ago 24
JSON Question

Script does not work locally but does on server

I am just starting out with javascript and well, I am stuck and it's quite embarrassing too.

First I tried to load a local json file which would not work. I found out about that quite fast.

But when I fixed this mistake it's still not working.

What I do have is basically a copy of http://bl.ocks.org/mbostock/4339083 which works in my browser, while my attempt does not.

Now I have two files:

data.js

var json =
{
"name":"flare",
"children":
[
...


This is so I have my json ready without the need of a webserver

And I have an html file with the script:

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.node {
cursor: pointer;
}

.node circle {
fill: #fff;
stroke: steelblue;
stroke-width: 1.5px;
}

.node text {
font: 10px sans-serif;
}

.link {
fill: none;
stroke: #ccc;
stroke-width: 1.5px;
}

</style>
<body>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="data.js"></script>
<script>
alert("here");

var margin = {top: 20, right: 120, bottom: 20, left: 120},
width = 960 - margin.right - margin.left,
height = 800 - margin.top - margin.bottom;

var i = 0,
duration = 750,
root;

var tree = d3.layout.tree()
.size([height, width]);

var diagonal = d3.svg.diagonal()
.projection(function(d) { return [d.y, d.x]; });

var svg = d3.select("body").append("svg")
.attr("width", width + margin.right + margin.left)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

alert("there");

d3.json(json, function(error, flare) {
if (error) throw error;

root = flare;
root.x0 = height / 2;
root.y0 = 0;

function collapse(d) {
if (d.children) {
d._children = d.children;
d._children.forEach(collapse);
d.children = null;
}
}

root.children.forEach(collapse);
update(root);
});

d3.select(self.frameElement).style("height", "800px");

function update(source) {

// Compute the new tree layout.
var nodes = tree.nodes(root).reverse(),
links = tree.links(nodes);

// Normalize for fixed-depth.
nodes.forEach(function(d) { d.y = d.depth * 180; });

// Update the nodes…
var node = svg.selectAll("g.node")
.data(nodes, function(d) { return d.id || (d.id = ++i); });

// Enter any new nodes at the parent's previous position.
var nodeEnter = node.enter().append("g")
.attr("class", "node")
.attr("transform", function(d) { return "translate(" + source.y0 + "," + source.x0 + ")"; })
.on("click", click);

nodeEnter.append("circle")
.attr("r", 1e-6)
.style("fill", function(d) { return d._children ? "lightsteelblue" : "#fff"; });

nodeEnter.append("text")
.attr("x", function(d) { return d.children || d._children ? -10 : 10; })
.attr("dy", ".35em")
.attr("text-anchor", function(d) { return d.children || d._children ? "end" : "start"; })
.text(function(d) { return d.name; })
.style("fill-opacity", 1e-6);

// Transition nodes to their new position.
var nodeUpdate = node.transition()
.duration(duration)
.attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; });

nodeUpdate.select("circle")
.attr("r", 4.5)
.style("fill", function(d) { return d._children ? "lightsteelblue" : "#fff"; });

nodeUpdate.select("text")
.style("fill-opacity", 1);

// Transition exiting nodes to the parent's new position.
var nodeExit = node.exit().transition()
.duration(duration)
.attr("transform", function(d) { return "translate(" + source.y + "," + source.x + ")"; })
.remove();

nodeExit.select("circle")
.attr("r", 1e-6);

nodeExit.select("text")
.style("fill-opacity", 1e-6);

// Update the links…
var link = svg.selectAll("path.link")
.data(links, function(d) { return d.target.id; });

// Enter any new links at the parent's previous position.
link.enter().insert("path", "g")
.attr("class", "link")
.attr("d", function(d) {
var o = {x: source.x0, y: source.y0};
return diagonal({source: o, target: o});
});

// Transition links to their new position.
link.transition()
.duration(duration)
.attr("d", diagonal);

// Transition exiting nodes to the parent's new position.
link.exit().transition()
.duration(duration)
.attr("d", function(d) {
var o = {x: source.x, y: source.y};
return diagonal({source: o, target: o});
})
.remove();

// Stash the old positions for transition.
nodes.forEach(function(d) {
d.x0 = d.x;
d.y0 = d.y;
});
}

// Toggle children on click.
function click(d) {
if (d.children) {
d._children = d.children;
d.children = null;
} else {
d.children = d._children;
d._children = null;
}
update(d);
}

</script>


as you can see it's now basically a 1:1 copy.

When I open that .html file though, my page stays blank.

How can this be? I understand that this would happen if I'd try to load a local .json file via the
d3.json
as that would try doing a http request, which would fail without a webserver to handle it.

But now that the json data is saved in a variable this behaviour makes no sense to me.

Please enlighten me! I'm trying to figure this out for a while now.

Answer

d3.json(url[, callback]) creates a request for the JSON file at the specified URL with the default mime type application/json. In your code you pass the JSON object instead of a URL. Please try this:

d3.json(json, function(error, flare)

and assign json from data.json to root:

//d3.json(json, function(error, flare) { <-- this will be removed
//if (error) throw error; <-- remove this too not needed !
root = json;
root.x0 = height / 2;
root.y0 = 0;

function collapse(d) {
    if (d.children) {
        d._children = d.children;
        d._children.forEach(collapse);
        d.children = null;
    }
}
root.children.forEach(collapse);
update(root);
//} <-- don't forget the closing brace.
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