dist/jspdf.node.debug.js
function calculateFontSpace(text, formObject, fontSize) {
    var font = scope.internal.getFont(formObject.fontName, formObject.fontStyle);
    var width = scope.getStringUnitWidth(text, {
      font: font,
      fontSize: parseFloat(fontSize),
      charSpace: 0
    }) * parseFloat(fontSize);
    var height = scope.getStringUnitWidth("3", {
      font: font,
      fontSize: parseFloat(fontSize),
      charSpace: 0
    }) * parseFloat(fontSize) * 1.5;
    return {
      height: height,
      width: width
    };
  }
function calculateFontSpace(text, formObject, fontSize) {
    var font = scope.internal.getFont(formObject.fontName, formObject.fontStyle);
    var width = scope.getStringUnitWidth(text, {
      font: font,
      fontSize: parseFloat(fontSize),
      charSpace: 0
    }) * parseFloat(fontSize);
    var height = scope.getStringUnitWidth("3", {
      font: font,
      fontSize: parseFloat(fontSize),
      charSpace: 0
    }) * parseFloat(fontSize) * 1.5;
    return {
      height: height,
      width: width
    };
  }
Small workaround for calculating the TextMetric approximately.

@param text
@param fontsize
@returns {TextMetrics} (Has Height and Width)