angular scroll event on div chang width

Angular Scroll Event on Div Changing Width

Have you ever encountered a scenario where you need to change the width of a <div> element based on the scroll position of the user? In this blog post, we will explore how to achieve this using Angular.

Step 1: Add Event Listener

The first step is to add an event listener to the <div> element that will trigger whenever the user scrolls. We can achieve this using Angular's @HostListener decorator.

import { Component, HostListener } from '@angular/core';

@Component({
  selector: 'app-scroll-div',
  template: '<div [ngStyle]="{width: divWidth}"></div>',
})
export class ScrollDivComponent {
  divWidth = '100px';

  @HostListener('window:scroll', ['$event'])
  onWindowScroll(event) {
    // Update div width here
  }
}

In the code above, we have created a new Angular component ScrollDivComponent and added an event listener using the @HostListener decorator. The 'window:scroll' argument tells Angular to listen for scroll events on the window object. We have also defined a property divWidth that will hold the current width of our <div> element.

Step 2: Update Width Based on Scroll Position

The next step is to update the width of our <div> element based on the scroll position of the user. We can achieve this by calculating the percentage of the user's scroll position and multiplying it with the desired maximum width.

import { Component, HostListener } from '@angular/core';

@Component({
  selector: 'app-scroll-div',
  template: '<div [ngStyle]="{width: divWidth}"></div>',
})
export class ScrollDivComponent {
  divWidth = '100px';
  maxWidth = 500;

  @HostListener('window:scroll', ['$event'])
  onWindowScroll(event) {
    const scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
    const scrollHeight = document.documentElement.scrollHeight || document.body.scrollHeight;
    const clientHeight = document.documentElement.clientHeight || window.innerHeight;

    const scrollPercentage = (scrollTop / (scrollHeight - clientHeight)) * 100;
    const newWidth = (scrollPercentage * this.maxWidth) / 100;

    this.divWidth = `${newWidth}px`;
  }
}

In the code above, we have added a new property maxWidth that will hold the maximum width of our <div> element. We have also defined a new function onWindowScroll that will be called whenever the user scrolls.

Inside the onWindowScroll function, we first calculate the user's scroll position using the window.pageYOffset and document.documentElement.scrollTop properties. We also calculate the total scroll height and the client height of the page using the document.documentElement.scrollHeight, document.body.scrollHeight, document.documentElement.clientHeight, and window.innerHeight properties.

We then calculate the percentage of the user's scroll position using the formula scrollTop / (scrollHeight - clientHeight) * 100. We then multiply this percentage with the maxWidth property to get the new width of our <div> element.

Finally, we update the divWidth property with the new width and Angular will automatically update the <div> element on the page.

Conclusion

In this blog post, we have learned how to change the width of a <div> element based on the user's scroll position using Angular. We have used Angular's @HostListener decorator to add a scroll event listener to the window object and calculated the percentage of the user's scroll position to update the width of our <div> element.