Create cache.js

themes/icarus/util/cache.js

@@ -0,0 +1,48 @@
+/**
+ * View cache utility functions.
+ * @module util/cache
+ */
+const crypto = require('crypto');
+const { Component } = require('inferno'); // eslint-disable-line no-unused-vars
+const { createElement } = require('inferno-create-element');
+
+const cache = {};
+
+function computeHash(props) {
+  return crypto.createHash('md5').update(JSON.stringify(props)).digest('hex');
+}
+
+module.exports = {
+  /**
+   * Create cached component from a given component class.
+   * The cache ID is caculated from the input props.
+   *
+   * @param {Component}   type        JSX component class
+   * @param {string}      prefix      Cache ID prefix
+   * @param {Function}    transform   Transform the input props to target props and
+   *                                  its result is used to compute cache ID
+   * @returns The new cachable functional component, which uses the <code>transform</code> function and the
+   *          component props to calculate the cache ID.
+   * <br>
+   *          The cache ID will be used to determine whether the same element with the exact same
+   *          props has been created and cached. If so, the cached element will be returned.
+   *          If the cache ID can be computed, a new element will be created use the
+   *          <code>createElement</code> function of the inferno.js, then it will be cached and returned.
+   *          If the <code>transform</code>ed props is empty (<code>!transform(props)</code>), the cachable
+   *          functional component will also return null element when <code>createElement</code> is called
+   *          on it.
+   */
+  cacheComponent(type, prefix, transform) {
+    return (props) => {
+      const targetProps = transform(props);
+      if (targetProps === null || typeof targetProps !== 'object') {
+        return null;
+      }
+      const cacheId = prefix + '-' + computeHash(targetProps);
+      if (!cache[cacheId]) {
+        cache[cacheId] = createElement(type, targetProps);
+      }
+      return cache[cacheId];
+    };
+  },
+};