refactor: server code (#2545)

+ Remove duplicated await
+ Replace some legacy codes with ES6
+ Fix some of eslint problems

server/modules/rendering/html-image-prefetch/renderer.js

@@ -17,7 +17,7 @@ const prefetch = async (element) => {
   const contentType = response.headers[`content-type`]
   const image = Buffer.from(response.body).toString('base64')
   element.attr('src', `data:${contentType};base64,${image}`)
-  element.removeClass('prefetch-candidate');
+  element.removeClass('prefetch-candidate')
 }
 
 module.exports = {

server/modules/rendering/markdown-core/underline.js

@@ -1,12 +1,12 @@
 const renderEm = (tokens, idx, opts, env, slf) => {
-  const token = tokens[idx];
+  const token = tokens[idx]
   if (token.markup === '_') {
-    token.tag = 'u';
+    token.tag = 'u'
   }
-  return slf.renderToken(tokens, idx, opts);
+  return slf.renderToken(tokens, idx, opts)
 }
 
 module.exports = (md) => {
-  md.renderer.rules.em_open = renderEm;
-  md.renderer.rules.em_close = renderEm;
+  md.renderer.rules.em_open = renderEm
+  md.renderer.rules.em_close = renderEm
 }

server/modules/rendering/markdown-kroki/renderer.js

@@ -73,13 +73,8 @@ module.exports = {
             continue
           }
 
-          var closeMarkerMatched = true
-          for (i = 0; i < closeMarker.length; ++i) {
-            if (closeMarker[i] !== state.src[start + i]) {
-              closeMarkerMatched = false
-              break
-            }
-          }
+          const i = closeMarker.findIndex(item => item !== state.src[start + i])
+          const closeMarkerMatched = i !== -1
 
           if (!closeMarkerMatched) {
             continue

server/modules/rendering/markdown-plantuml/renderer.js

@@ -74,13 +74,8 @@ module.exports = {
             continue
           }
 
-          var closeMarkerMatched = true
-          for (i = 0; i < closeMarker.length; ++i) {
-            if (closeMarker[i] !== state.src[start + i]) {
-              closeMarkerMatched = false
-              break
-            }
-          }
+          const i = closeMarker.findIndex(item => item !== state.src[start + i])
+          const closeMarkerMatched = i !== -1
 
           if (!closeMarkerMatched) {
             continue
@@ -112,7 +107,7 @@ module.exports = {
           altToken
         )
 
-        var zippedCode = encode64(zlib.deflateRawSync('@startuml\n' + contents + '\n@enduml').toString('binary'))
+        const zippedCode = encode64(zlib.deflateRawSync('@startuml\n' + contents + '\n@enduml').toString('binary'))
 
         token = state.push('uml_diagram', 'img', 0)
         // alt is constructed from children. No point in populating it here.