[Plot] Add JSDoc

Add inline comments to Plot scripts. WTD-533.

platform/features/plot/src/elements/PlotAxis.js

@@ -5,10 +5,30 @@ define(
     function () {
         "use strict";
 
+        /**
+         * A PlotAxis provides a template-ready set of options
+         * for the domain or range axis, sufficient to populate
+         * selectors.
+         *
+         * @constructor
+         * @param {string} axisType the field in metadatas to
+         *        look at for axis options; usually one of
+         *        "domains" or "ranges"
+         * @param {object[]} metadatas metadata objects, as
+         *        returned by the `getMetadata()` method of
+         *        a `telemetry` capability.
+         * @param {object} defaultValue the value to use for the
+         *        active state in the event that no options are
+         *        found; should contain "name" and "key" at
+         *        minimum.
+         *
+         */
         function PlotAxis(axisType, metadatas, defaultValue) {
             var keys = {},
                 options = [];
 
+            // Look through all metadata objects and assemble a list
+            // of all possible domain or range options
             function buildOptionsForMetadata(m) {
                 (m[axisType] || []).forEach(function (option) {
                     if (!keys[option.key]) {
@@ -24,7 +44,18 @@ define(
             // template, so expose properties directly to facilitate
             // two-way data binding (for drop-down menus)
             return {
+                /**
+                 * The set of options applicable for this axis;
+                 * an array of objects, where each object contains a
+                 * "key" field and a "name" field (for machine- and
+                 * human-readable names respectively)
+                 */
                 options: options,
+                /**
+                 * The currently chosen option for this axis. An
+                 * initial value is provided; this will be updated
+                 * directly form the plot template.
+                 */
                 active: options[0] || defaultValue
             };
         }