Angular PrimeNG Form TreeSelect Events

Angular PrimeNG is an open-source library that consists of native Angular UI components that are used for great styling and this framework is used to make responsive websites with very much ease. In this article, we will be seeing the Angular PrimeNG Form TreeSelect Events.

The TreeSelect Component allows the users to select items from hierarchical data. It accepts an array of TreeNodes as its options property to show the data.

Angular PrimeNG Form TreeSelect Events:

• onShow: When the overlay is shown, a callback is triggered.
• onHide: When the overlay is hidden, a callback is triggered.
• onFilter: When the data is filtered, a callback is triggered.
• onNodeSelect: When the node is selected, a callback is triggered.
• onNodeUnselect: When the node is unselected, a callback is triggered.
• onNodeExpand: When the node is expanded, a callback is triggered.
• onNodeCollapse: When the node is collapsed, a callback is triggered.
• onClear: When an input field is cleared, a callback is triggered.

Syntax:

<p-treeSelect 
    (event)=function()>
</p-treeSelect>

Creating Angular application & module installation:

Step 1: Create an Angular application using the following command.

ng new appname

Step 2: After creating your project folder i.e. appname, move to it using the following command.

cd appname

Step 3: Install PrimeNG in your given directory.

npm install primeng --save
npm install primeicons --save

Project Structure: It will look like the following

Steps to run the application: Run the below command to see the output

ng serve --save

Example 1: In this example, we will learn about Angular PrimeNG Form TreeSelect Events onNodeExpand.

• app.component.html:

HTML

<h1 style="color: green;">GeeksforGeeks</h1>
<h2>Angular PrimeNG Form TreeSelect Events</h2>

<p-treeSelect
    [(ngModel)]="selected"
    selectionMode="single"
    [options]="nodes"
    placeholder="Select a Node"
    (onNodeExpand)="onNodeExpand()">
</p-treeSelect>

• app.component.ts:

Javascript

import { Component } from "@angular/core";
import { TreeNode } from "primeng/api";

@Component({
    selector: "app-root",
    templateUrl: "./app.component.html"
})

export class AppComponent {
    nodes: TreeNode[] = [];
    selected: any;
    onNodeExpand() {
        alert("Node is Expanded");
    }
    ngOnInit() {
        this.nodes = [
            {
                label: "Work",
                icon: "pi pi-folder",
                children: [
                    {
                        label: "data.json",
                        icon: "pi pi-file"
                    },
                    {
                        label: "sales.docx",
                        icon: "pi pi-file"
                    },
                    {
                        label: "presentation.pptx",
                        icon: "pi pi-file"
                    }
                ]
            },
            {
                label: "Home",
                icon: "pi pi-folder",
                children: [
                    {
                        label: "grocery.word",
                        icon: "pi pi-file"
                    },
                    {
                        label: "picture.jpeg",
                        icon: "pi pi-file"
                    },
                    {
                        label: "homeplan.png",
                        icon: "pi pi-file"
                    }
                ]
            },
            {
                label: "Multimedia",
                icon: "pi pi-folder",
                children: [
                    {
                        label: "infinity-war.mp4",
                        icon: "pi pi-file"
                    },
                    {
                        label: "you.mp3",
                        icon: "pi pi-file"
                    },
                    {
                        label: "endgame.mp4",
                        icon: "pi pi-file"
                    },
                    {
                        label: "MI.mp4",
                        icon: "pi pi-file"
                    }
                ]
            }
        ];
    }
}

• app.module.ts:

Javascript

import { NgModule } from "@angular/core";
import { BrowserAnimationsModule }
    from "@angular/platform-browser/animations";
import { AppComponent } from "./app.component";
import { FormsModule } from "@angular/forms";
import { TreeSelectModule } from "primeng/treeselect";

@NgModule({
    imports: [
        BrowserAnimationsModule,
        TreeSelectModule,
        FormsModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})

export class AppModule {}

Output:

Example 2: In this example, we will learn about Angular PrimeNG Form TreeSelect Events onNodeCollapse.

• app.component.html:

HTML

<h1 style="color:green">GeeksforGeeks</h1>
<h2>Angular PrimeNG Form TreeSelect Events</h2>

<p-treeSelect
    [(ngModel)]="selected"
    selectionMode="single"
    [options]="nodes"
    placeholder="Select a Node"
    (onNodeCollapse)=onNodeCollapse()>
</p-treeSelect>

• app.component.ts:

Javascript

import { Component } from "@angular/core";
import { TreeNode } from "primeng/api";

@Component({
    selector: "app-root",
    templateUrl: "./app.component.html",
})

export class AppComponent {
    nodes: TreeNode[] = [];
    selected: any;
    onNodeCollapse(){
        alert("Node is Collapsed")
    }
    ngOnInit()
    {
        this.nodes = [
            {
                "label": "Work",
                "icon": "pi pi-folder",
                "children": [
                    {
                        "label": "data.json",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "sales.docx",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "presentation.pptx",
                        "icon": "pi pi-file"
                    }
                ]
            },
            {
                "label": "Home",
                "icon": "pi pi-folder",
                "children": [
                    {
                        "label": "grocery.word",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "picture.jpeg",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "homeplan.png",
                        "icon": "pi pi-file"
                    }
                ]
            },
            {
                "label": "Multimedia",
                "icon": "pi pi-folder",
                "children": [
                    {
                        "label": "infinity-war.mp4",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "you.mp3",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "endgame.mp4",
                        "icon": "pi pi-file"
                    },
                    {
                        "label": "MI.mp4",
                        "icon": "pi pi-file"
                    }
                ]
            }
        ];
    }
}

• app.module.ts:

Javascript

import { NgModule } from "@angular/core";
import { BrowserAnimationsModule }
    from "@angular/platform-browser/animations";
import { AppComponent } from "./app.component";
import { FormsModule } from "@angular/forms";
import { TreeSelectModule } from "primeng/treeselect";

@NgModule({
    imports: [
        BrowserAnimationsModule,
        TreeSelectModule,
        FormsModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})

export class AppModule {}

Output:

Reference: https://primefaces.org/primeng/treeselect