Add initial versions

fetch-mixin.js

@@ -0,0 +1,71 @@
+export const fetchMixin = function(superClass) {
+  return class extends superClass {
+    constructor() {
+      super();
+      this.__abortControllers = new Map();
+    }
+
+    get(url) {
+      return fetch(url).then(response => response.json());
+    }
+
+    head(url) {
+      return fetch(url, { method: 'HEAD' });
+    }
+
+    async post(url, data, overwrite = true) {
+      this.__cancelRunningRequest(url);
+
+      if (overwrite === true) {
+        const ac = new AbortController();
+        this.__abortControllers.set(url, ac);
+      }
+
+      try {
+        const reqOptions = {
+          method: 'POST',
+          signal: this.__abortControllers.get(url).signal,
+          mode: 'cors',
+          cache: 'no-cache',
+          headers: {
+            'Content-Type': 'application/json; charset=utf-8'
+          },
+          referrer: 'no-referrer',
+          body: JSON.stringify(data)
+        };
+
+        document.dispatchEvent(new CustomEvent('before-request', { detail: reqOptions, bubbles: true, composed: true }));
+
+        const result = await fetch(url, reqOptions).then(response => response.json());
+
+        this.__abortControllers.delete(url);
+
+        if (result.statusCode === 500) {
+          console.error(result);
+        }
+
+        return result;
+      } catch (err) {
+        if (err.name === 'AbortError') {
+          return { statusCode: -1, error: err };
+        } else {
+          this.__abortControllers.delete(url);
+          return { statusCode: null, error: err };
+        }
+      }
+    }
+
+    isInFlight(url) {
+      return Boolean(this.__abortControllers.get(url));
+    }
+
+    __cancelRunningRequest(url) {
+      if (this.__abortControllers.has(url)) {
+        try {
+          this.__abortControllers.get(url).abort();
+        } catch (err) { }
+        this.__abortControllers.delete(url);
+      }
+    }
+  };
+};