Simple line chart

CSS

body {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.x.axis path {
  display: none;
}

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

JavaScript

var data = [{
    "key": [2000, 1, 1, 12],
    "value": 1000
}, {
    "key": [2000, 2, 1, 12],
    "value": 3896
}, {
    "key": [2000, 7, 1, 24],
    "value": 289
}, {
    "key": [2000, 8, 1, 24],
    "value": 389
}]

var margin = {
        top: 20,
        right: 20,
        bottom: 30,
        left: 50
    },
    width = 760 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var parseDate = d3.time.format("%Y.%m.%d.%H").parse;

var x = d3.time.scale()
    .range([0, width]);

var y = d3.scale.linear()
    .range([height, 0]);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left");

var line = d3.svg.line()
    .x(function(d) {
        return x(d.date);
    })
    .y(function(d) {
        return y(d.value);
    });

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

var mapped_data = data.map(function(d) {
    return {
        date: 4,
        value: +d.value
    }
});
console.log(mapped_data);

x.domain(d3.extent(mapped_data, function(d) {
    return d.date;
}));
y.domain(d3.extent(mapped_data, function(d) {
    return d.value;
}));

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis);

svg.append("g")
    .attr("class", "y axis")
    .call(yAxis)
    .append("text")
    .attr("transform", "rotate(-90)")
    .attr("y", 6)
    .attr("dy", ".71em");

svg.append("path")
    .datum(mapped_data)
    .attr("class", "line")
    .attr("d", line);