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How to run page specific javascript on Rails

In Ruby on Rails, all your javascript is available everywhere, but we always want to run some javascript only on certain pages. This is how I manage to run and compartiment my javascript code based on models and actions.

First you need to add to your html layout a way for javascript to detect which model and which action the page is rendering:

html app/views/layouts/application.html.erb <body data-controller="<%= controller_name %>" data-action="<%= action_name %>"> Then in your main javascript file:

javascript app/assets/application.js //= require jquery //= require jquery_ujs //= require ./init //= require ./utils // = require_tree ./ressources

We define the code that will be run on every page at initialisation:

“` javascript app/assets/init.js

// init your global app object

// you need to add your controllers here to not throw an error

// when calling the exec function from the utils.js file

window.YOURAPP = { common: {}, users: {}, anothercontroller:{} };

YOUR_APP.common.init = function() {

console.log("this will run on every page”);

} “`

I usually add a UTIL object where I put my utilities functions, for this example, there are two functions that interest us "init” and “exec”:

“` javascript app/assets/utils.js var window.UTIL = { // execute the corresponding function exec: function (controller, action) { var ns = window.YOUR_APP; if (!action){ var action = "init”; } if ( controller != “” && ns[controller] && typeof ns[controller][action] == “function” ){ ns[controller]action; } },

// run on every page load to init the javascript calls init: function(){ var body = document.body; var controller = body.getAttribute(“data-controller”); var action = body.getAttribute(“data-action”) UTIL.exec(“common”) //run common.init UTIL.exec(controller) //run controller.init UTIL.exec(controller, action) //run controller.action } };

//run the init function $( document ).ready(UTIL.init)

And then inside my directory app/assets/ressources I have one js file per model with for example for the user model something like that:

``` javascript app/assets/ressources/user.js
YOUR_APP.users = {
  init: function() { alert("this code run on all pages for user's action"); },
  index: function() { alert("this code run only on the user index page"); },
  view: function() { alert("this code run only on the user view page"); },
  edit: function() { alert("this code run only on the user edit page"); },
  show: function() { alert("this code run only on the user show page"); }

I hope this will be useful for those who are looking for a solution. It’s not the best but it works and gets things separated.

Loic Ginoux

Développeur freelance full-stack avec 9 ans d'expérience, spécialisé sur les applications web, e-commerce, Ruby on Rails et frameworks Javascript tels que React ou Angular.

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