Improve NodeJS example

Fixes RelaxedJS/ReLaXed#147
Fixes RelaxedJS/ReLaXed#148
Fixes RelaxedJS/ReLaXed#149

README.md

@@ -158,50 +158,61 @@ ReLaXed consists of a few lines of code binding together other software. It uses
 An Example: 
 
 ```javascript
-
 const { masterToPDF } = require('relaxedjs');
 const puppeteer = require('puppeteer');
 const plugins = require('relaxedjs/src/plugins');
+const path = require('path');
 
 class HTML2PDF {
-    constructor(){
-        this.puppeteerConfig = {
-            headless: true,
-            args: [
-                '--no-sandbox',
-                '--disable-translate',
-                '--disable-extensions',
-                '--disable-sync'
-            ],
-        };
-
-        this.relaxedGlobals = {
-            busy: false,
-            config: {},
-            configPlugins: [],
-        };
+  constructor() {
+    this.puppeteerConfig = {
+      headless: true,
+      args: [
+        '--no-sandbox',
+        '--disable-translate',
+        '--disable-extensions',
+        '--disable-sync',
+      ],
+    };
+
+    this.relaxedGlobals = {
+      busy: false,
+      config: {},
+      configPlugins: [],
+    };
+
+    this._initializedPlugins = false;
+  }
+
+  async _initializePlugins() {
+    if (this._initializedPlugins) return; // Do not initialize plugins twice
+    for (const [i, plugin] of plugins.builtinDefaultPlugins.entries()) {
+      plugins.builtinDefaultPlugins[i] = await plugin.constructor();
     }
-
-    async _initializePlugins() {
-        for (let [i, plugin] of plugins.builtinDefaultPlugins.entries()) {
-            plugins.builtinDefaultPlugins[i] = await plugin.constructor();
-        }
-        await plugins.updateRegisteredPlugins(this.relaxedGlobals, '/');
-
-        let chrome = await puppeteer.launch(this.puppeteerConfig);
-        this.relaxedGlobals.puppeteerPage = await chrome.newPage();
-    }
-
-    async pdf(template_pug, json_data){
-        await this._initPDFReader();
-        
-        await masterToPDF(template_pug,
-            this.relaxedGlobals,
-            '<path-to-render-html>.htm',
-            '<path-to-render-pdf>.pdf',
-            json_data,
-        );
+    await plugins.updateRegisteredPlugins(this.relaxedGlobals, '/');
+
+    const chrome = await puppeteer.launch(this.puppeteerConfig);
+    this.relaxedGlobals.puppeteerPage = await chrome.newPage();
+    this._initializedPlugins = true;
+  }
+
+  async pdf(templatePath, json_data, tempHtmlPath, outputPdfPath) {
+    await this._initializePlugins();
+    if (this._initializedPlugins) {
+      // Paths must be absolute
+      const defaultTempHtmlPath = tempHtmlPath || path.resolve('temp.html');
+      const defaultOutputPdfPath =
+        outputPdfPath || path.resolve('output.pdf');
+
+      await masterToPDF(
+        templatePath,
+        this.relaxedGlobals,
+        defaultTempHtmlPath,
+        defaultOutputPdfPath,
+        json_data
+      );
     }
+  }
 }
 
 module.exports = new HTML2PDF();
@@ -211,7 +222,6 @@ Usage:
 ```javascript
 const HTML2PDF = require('./HTML2PDF.js');
 (async () => {
-    await HTML2PDF._initializePlugins();
     await HTML2PDF.pdf('./template.pug', {"a":"b", "c":"d"});
 })();
 ```