What is the correct syntax of ng-include?

The most common and correct syntax for using ng-include is:

<div ng-include="'path/to/template.html'"></div>

Notice the single quotes inside the double quotes—this tells AngularJS to treat the string as a literal path. You can also use a scope variable if the URL is stored in your controller, for example:

<div ng-include="dynamicTemplateUrl"></div>

where dynamicTemplateUrl is defined in your controller.

Detailed Explanation

Literal Path
```
<div ng-include="'templates/header.html'"></div>
```
- AngularJS will fetch and render the templates/header.html file into this <div>.
- Be mindful of the inner quotes—it must be 'path/to/file.html', not path/to/file.html.
Scope Variable
```
<div ng-include="templateUrl"></div>
```
- Here, templateUrl is a variable in your controller’s scope:
```
$scope.templateUrl = 'templates/header.html';
```
- AngularJS will dynamically load whatever path is stored in templateUrl.
Optional Callbacks
- You can specify an onload expression to run logic once the template is loaded:
```
<div ng-include="'templates/header.html'" onload="initHeader()"></div>
```
- This can be handy if you need to initialize something after the included template is rendered.
Single vs. Multiple Includes
- You can use ng-include multiple times across your application to load partials or shared UI elements, but each instance should reference its own path or scope variable.
Error Handling
- If the template URL is incorrect or the file fails to load, AngularJS may log a 404 error in the console. Ensure your paths are correct and that the server is serving the files properly.

Best Practices

Keep Partials Small
- Break down large templates into smaller, more maintainable partials. This also helps AngularJS load only what’s needed.
Lazy Loading
- If you’re dealing with many partials, consider lazy loading or caching strategies (like $templateCache) to improve performance.
Consistent Naming
- Use a clear folder structure (e.g., /partials, /templates) and consistent naming for easier discovery.

Leveling Up Your AngularJS & JavaScript Skills

Using ng-include effectively is just one piece of building maintainable AngularJS applications. If you want to strengthen your core JavaScript and system design abilities, here are some resources from DesignGurus.io:

Grokking JavaScript Fundamentals
Sharpen your JavaScript fundamentals—closures, prototypes, async patterns—to write clean, optimized AngularJS code.
Grokking the Coding Interview: Patterns for Coding Questions
Prepare for real coding interviews using pattern-based solutions—a skill that benefits front-end and full-stack developers alike.
Grokking the System Design Interview
As your AngularJS app grows, you’ll need to consider performance, scalability, caching, and more. System design knowledge is critical for large-scale applications.

For personalized feedback, consider their Mock Interviews (Coding Mock Interview or System Design Mock Interview) with ex-FAANG engineers. Check out the DesignGurus.io YouTube Channel for free tutorials, too.

Final Thoughts

The correct syntax for ng-include usually involves single quotes inside double quotes to specify a template path, like:

<div ng-include="'templates/header.html'"></div>

or a scope variable in your controller:

<div ng-include="myTemplateVariable"></div>

This directive is excellent for modularizing your AngularJS application, letting you compose your UI from reusable partials while keeping your code neat and organized.

CONTRIBUTOR

TechGrind