helper function $

scripts/background/extractor.js

@@ -15,7 +15,6 @@ class Extractor {
     task(...args) {
         if (!testArgs(...args)) {
             console.log(`Invalid task arguments: ${argsToString(...args)}\n\n${signitures}\n`);
-            // break call chain to avoid unexpected task running
             return this;
         }
         // given >2 arguments means the task specifies target page, 
@@ -31,6 +30,7 @@ class Extractor {
     clear() {
         this._tasks = [];
         this._results = [];
+        return this;
     }
     /**
      * Start the task chain.
@@ -64,6 +64,7 @@ class Extractor {
             result => {
                 this._results[this._tasks[this._tasks.length - 1]] = result;
                 this._running = false;
+                console.log("Tasks are all done.")
                 this.save();
             }
         ).catch(err => {
@@ -122,9 +123,16 @@ class Extractor {
             console.log(`No result for task #${taskid}. Forget to call ".start()"?`);
             return;
         }
-        if (confirm(
-                `Click confirm to download if the sample data looks good (${result.data.length} items)：\n\n${result.toString(50) || "- Empty -"}`
-            )) {
+        if (result.data.length <= 1) { // 1 for selector headers
+            console.log(`No result for task #${taskid}. Forget to call ".start()"?`);
+            return;
+        }
+        let msg = `
+Please confirm to download (${result.data.length - 1} items)：
+
+${result.toString(50) || "- Empty -"}
+`.trim();
+        if (confirm(msg)) {
             saveFile(result, "text/csv");
         }
     }

scripts/background/helpers.js

@@ -0,0 +1,3 @@
+function $(...args) {
+    return new Extractor().task(...args).start();
+}

scripts/background/signiture.js

@@ -1,17 +1,21 @@
 const signitures = `
 ## Usage
-new Extractor().task(...args).task(...args).start();
+// single task
+$(...args);
+// managed task chains
+e = new Extractor();
+e.task(...args).task(...args).start();
 
-## Extractor.task() Signitures:
-function(itemsSelector:string, fieldSelectors:string[])
-function(itemsSelector:string, fieldSelectors:string[], url:string, from:number, to:number, interval:number)
-function(itemsSelector:string, fieldSelectors:string[], url:string, pages:number[])
-function(itemsSelector:string, fieldSelectors:string[], urls:string[])
+## Task Call Signitures:
+function(itemsSelector:string, fieldSelectors:string[]);
+function(itemsSelector:string, fieldSelectors:string[], url:string, from:number, to:number, interval:number);
+function(itemsSelector:string, fieldSelectors:string[], url:string, pages:number[]);
+function(itemsSelector:string, fieldSelectors:string[], urls:string[]);
 
 ## Example:
 // extract all links text & url under '.item' elements
 // use 'selector@attr' to get attribute of the field elements
-new Extractor().task(".item", ["a", "a@href"]).start();
+$(".item", ["a", "a@href"]);
 
 ## See Detailed Help:
 https://git.jebbs.co/jebbs/data-extracter-extesion