Added show_empty option (#2)

README.md

@@ -10,6 +10,7 @@ This element is **not** all that useful as a card (it can be used for that to),
 | entity | string | **Required** | The entity_id of the entity you want to show.
 | attribute | string | **Required** | The attribute of the entity you want to show.
 | prefix | string | **Optional** | A string you want to show in front of the attribute, ex. "My prefix string: "
+| show_empty | boolean | **Optional** | Give you the possibility to show `unavailable` if the state is empty, default `false`
 
 ## Installation
 

VERSION

@@ -1 +1 @@
-0.0.2
+0.0.3

state-attribute-element.js

@@ -2,13 +2,22 @@ class StateAttributeElement extends HTMLElement {
   set hass(hass) {
     const entityId = this.config.entity;
     const prefix_string = this.config.prefix
+    const show_empty = this.config.show_empty
     const attr = this.config.attribute;
     const state = hass.states[entityId].attributes[attr];
     const card = document.createElement('state-attribute-element');
-    if (prefix_string) {
-      this.innerHTML = prefix_string + state;
-    } else {
-      this.innerHTML = state;
+    if (state != null) {
+      if (prefix_string) {
+        this.innerHTML = prefix_string + state;
+      } else {
+        this.innerHTML = state;
+      }
+    } else if (show_empty == true) {
+      if (prefix_string) {
+        this.innerHTML = prefix_string + state;
+      } else {
+        this.innerHTML = state;
+      }
     }
   }
   setConfig(config) {
@@ -18,6 +27,9 @@ class StateAttributeElement extends HTMLElement {
     if (!config.attribute) {
       throw new Error('You need to define an attribute');
     }
+    if (!config.show_empty) {
+      config.show_empty = false;
+    }
     this.config = config;
   }