![]() ![]() Where did it put it, and how does Javascript find it? npm install is a command that lets you download packages from their repository. NPM is a package repository service that hosts published JavaScript modules. Browsers do not implement this module system.Īlso, before I got it to work in node, I had to do npm install pg. Require(), module.exports and exports are APIs of a module system that is specific to Node.js. Why does it work in node but not in a webpage? This allows your code to access functionality of the PostgreSQL client's APIs via the pg variable. In your code, var pg = require('pg') loads the pg module, a PostgreSQL client for Node.js. For a module to access another module's exports or module.exports, it must use require(). To expose things from a module, they must be assigned to exports or module.exports. A module cannot directly access things defined in another module unless it chooses to expose them. In Node.js, each module has its own scope. Any script can freely define/modify/remove/call anything on the global scope. When they execute, they all have direct access to the global scope, a "shared space" among all scripts. In browser JavaScript, scripts are added via the element. One big difference between Node.js modules and browser JavaScript is how one script's code is accessed from another script's code. This concept is also present in other languages with minor differences in syntax and behavior, like C's include, Python's import, and so on. Modules are a way to split an application into separate files instead of having all of your application in one file. But in Node.js, it's a built-in function with a special purpose: to load modules. Require() is not part of the standard JavaScript API. Where did it put it, and how does JavaScript find it? What's that about? I looked in the directory and didn't find a file pg. So what is this "require"? Why does it work in Node but not in a webpage?Īlso, before I got it to work in Node, I had to do npm install pg. I checked on the JavaScript console and it just says "require not defined". ![]() Next I tried to make it run on a webpage, but nothing seemed to happen. can stream row results back 1 at a timeĬonsole.log("Beatle name: %s", row.name) //Beatle name: JohnĬonsole.log("Beatle birth year: %d", ()) //dates are returned as javascript datesĬonsole.log("Beatle height: %d' %d\"", Math.floor(row.height/12), row.height%12) //integers are returned as javascript ints Var query = client.query("SELECT * FROM beatles WHERE name = $1", ) subsequent queries with the same name will be executed without re-parsing the query plan by postgres Text: "INSERT INTO beatles(name, height, birthday) values($1, $2, $3)", or by passing an options object containing text, (optional) parameter values, and (optional) query name queries can be executed either via text/parameter values passed as individual arguments queries are queued and executed one after another once the connection becomes availableĬlient.query("CREATE TEMP TABLE beatles(name varchar(10), height integer, birthday timestamptz)") Ĭlient.query("INSERT INTO beatles(name, height, birthday) values($1, $2, $3)", ) Var conString = client = new pg.Client(conString) var pg = require('pg') //native libpq bindings = `var pg = require('pg').native` I was able to get the following sample code to run in Node. ![]() I'm trying to get JavaScript to read/write to a PostgreSQL database.
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