Edit in JSFiddle

var mihenkdata = {
    "xdata": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
    "ydata": [21, 18, 23, 16, 25, 20, 27, 35, 29, 18, 16, 26, 33, 19, 35],
    "opt": {
        "x_labels": [],
        "y_labels": [],
        "zoom": true,
        "xlab": "x label",
        "ylab": "y label",
        "color": [],
        "div_id": "graph5"
    }
}

mihenk.line(mihenkdata);

<!--Add d3.js-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js" charset="utf-8"></script>

<!--Add Mihenk JS and CSS -->
<link rel="stylesheet" href="../mihenk.css" />
<script src="../mihenk.js" ></script>

<!-- Download Svg and Png-->
<!-- pngindir('graph_div_id') ,  svgindir('graph_div_id') -->
<button onclick="pngindir('graph')" class="btn btn-default btn-sm pull-right" style="margin-top:3px;margin-right:5px;"><span class="fa fa-download" /> Png</button>
<button onclick="svgindir('graph')" class="btn btn-default btn-sm pull-right" style="margin-top:3px;margin-right:5px;"><span class="fa fa-download" /> Svg</button>

<!--Graphic-->
<div id='graph5'>
   <svg> </svg>
</div>