for (var i=0;i<node_set.length;i++){
    var n_x = node_set[i].x;
    var n_y = node_set[i].y;
    if (!adj_list[i+1]){
        adj_list[i+1] = [];
    }
    if (x <= n_x+10 && x >= n_x-10 && y <= n_y+10 && y >= n_y-10){
        if (!edge_started){
            s_x = n_x, s_y = n_y;
            glitter(s_x, s_y);
            ctx.beginPath();
            ctx.moveTo(n_x, n_y);
            edge_started = true;
            bgn_vertex = i+1;
        } else {
            draw_edge(n_x, n_y);
            glitter(s_x, s_y);
            edge_started = false;
            adj_list[bgn_vertex].push(node_set[i]["id"]);
            adj_list[node_set[i].id].push(node_set[bgn_vertex-1]["id"]);
        }
    }
}