php - Error when setting up y axis from a data table that is JSON. parsed for d3 charts -

i can't seem use projectdate field set x axis. use json.parse data json , prepared data using data.foreach used d3 chart. when call page, "uncaught typeerror: t.substring not function. please let me know doing wrong.

  // data viewmodel   var data = json.parse(<?php echo json_encode($viewmodel) ?>);    data.foreach(function(d) {       d.projectdate = parsedate(d.projectdate);       d.cost = +d.cost;   });     var y = d3.scale.linear()         .domain([0, d3.max(data, function(d){              return d.cost;         })])        .range([height, 0]);     var x = d3.scale.ordinal()             .domain(d3.extent(data, function(d){                 var date = parsedate(d.projectdate);                 return (date);             }))             .range([0, width]);      var ordinalcolorscale = d3.scale.category20();