How can I make JavaScript read/write to a PostgreSQL database in a web browser? The code I found on GitHub works in Node.js but not in a browser. It gives an error “Uncaught ReferenceError: require is not defined.” What is the “require” function, and why does it work in Node.js but not in a web browser? Also, what does “npm install pg” do, and where does it put the “pg” package for Node.js to find it?
Hey Heena,
It looks like you need to use require(), which is a function in Node.js that is used to load modules. It’s not a part of standard JavaScript. In Node.js, modules are used to split an application into separate files. Each module has its own scope, unlike in browser JavaScript, where scripts share a global scope.
When you use require('pg'), you’re loading the pg module, a PostgreSQL client for Node.js. This allows your code to access the PostgreSQL client’s APIs through the pg variable.
require() doesn’t work in a web browser because browsers do not implement the module system used in Node.js. Browsers use script tags to include scripts; all scripts share a global scope.
Before using require('pg') in Node.js, you must install the pg module using npm (Node Package Manager). npm is a package repository for JavaScript, and npm install is used to download packages from this repository. The downloaded modules are placed in a node_modules directory in your project.
In Node.js, modules are resolved using a set of rules. When you use require('pg'), Node.js looks for the pg module in the node_modules directory of your project. If it finds the module, it loads and returns it; otherwise, it throws an error.
Hey Heena,
You can add the script tag to the header to add the file just like we add the external CSS to the HTML header.
To load Node modules in a browser, you can use a script tag in your HTML file to reference the module’s file in the node_modules directory. For example, if your module is in a folder called node_modules at the root level of your project, you can load it like this:
You can use the script source tag and add this source: node_modules/module-name/module-file.js within the script tag
This will make the module’s functionality available in your browser application. Another approach is to use a module loader like RequireJS, which is popular for larger projects.
To make your scripts.js file available to the browser, you can use a module bundler like Webpack or Browserify. These tools will bundle all your JavaScript files, including node_modules, into a single file that can be included in your HTML.
First, install Webpack or Browserify globally using npm:
npm install -g webpack
or
npm install -g browserify
Next, in your project directory (xyz), create a configuration file named webpack.config.js or browserify.config.js, depending on which tool you’re using. Here’s an example configuration for Webpack:
const path = require('path');
module.exports = {
entry: './js/scripts.js',
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'dist'),
},
};
Then, run Webpack or Browserify to bundle your scripts:
For Webpack:
webpack
For Browserify:
browserify js/scripts.js -o dist/bundle.js
Finally, include the bundled script in your HTML file within the script tag:
dist/bundle.js
This will make your scripts.js file, along with its dependencies, available to the browser.