NgFor is a built-in directive in Angular which can be incredibly useful when you want to loop over the keys of a dictionary in your template file. In simple terms, it is used to iterate over an array or an object right inside the template. Angular provides a robust framework that assists multiple operations including data binding, component-based routing, dependency injection, and many others. Nevertheless, to have full control of these operations, the developer must understand how Angular handles these.
The structure of ngFor statement is: *ngFor = “let item of items; index as i”. Where ‘items’ is the iterable being looped over and ‘i’ is the index of the current item in the iteration.
Solution to Using NgFor on Keys of a Dictionary
Angular does not readily offer a solution to using ngFor on the keys of a dictionary. However, there is a simple enough way to obtain the desired result. One approach is to create an array of keys, which can then be iterated over in the DOM.
let dictionary = {
key1: 'value1',
key2: 'value2',
key3: 'value3',
};
let keys = Object.keys(dictionary);
In the HTML template file, you can use *ngFor to iterate over the keys array:
<div *ngFor="let key of keys">
{{ key }}: {{ dictionary[key] }}
</div>
Step-By-Step Explanation of the Code
Firstly, we need to know what an object in JavaScript is. It is an entity which holds unordered data in “key:value” pair. The Object.keys() method returns an array containing the object’s enumerable property keys. This operation is performed in this line of code:
let keys = Object.keys(dictionary);
In the HTML template, the Angular *ngFor is used to iterate over these keys:
<div *ngFor="let key of keys">
Each key will then access the associated value in the dictionary with the expression `dictionary[key]`.
Functions Involved
- Object.keys(): This is a JS method that returns an array of all enumerable properties of the object. When applied to a dictionary in this case, it basically provides the keys.
- *ngFor: This is an Angular structural directive that is used in the template to loop over a collection.
This method can be quite useful when trying to display the contents of a dictionary on your website. However, it is important to note that this will only work when the keys are strings, as they have to be valid property identifiers in JavaScript.
Keep in mind that Angular is incredibly flexible – while the method outlined here is one good solution, it may not be the only one. Depending on your specific requirements, you may need to adjust and adapt accordingly.
