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isElementInViewport.ts
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isElementInViewport.ts
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/*
* Copyright 2019 LABOR.digital
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Last modified: 2019.03.31 at 19:36
*/
import {isBrowser} from '../Environment/isBrowser';
import {isNumber} from '../Types/isNumber';
import {isUndefined} from '../Types/isUndefined';
import {getScrollPos} from './getScrollPos';
import {getViewportSize} from './getViewportSize';
export interface IsElementInViewportOptions
{
/**
* An additional offset from the top of the viewport to take into consideration
*/
offsetTop?: number;
/**
* By default the function returns true if the element is at least partially visible
* inside the viewport. If you set this to true the method will only return true if
* the element is completely visible and does not collide with the outer bounds.
*/
onlyFull?: boolean;
}
/**
* Checks if the given element is visible inside the current viewport (any part of it)
* @param el The element to heck for
* @param offsetTop An additional offset to check for
*/
export function isElementInViewport(el: HTMLElement, offsetTop?: number): boolean;
/**
* Checks if the given element is visible inside the current viewport (any part of it)
* @param el The element to heck for
* @param options Additional options
*/
export function isElementInViewport(el: HTMLElement, options?: IsElementInViewportOptions): boolean
export function isElementInViewport(el: HTMLElement, options?: number | IsElementInViewportOptions): boolean
{
if (!isBrowser()) {
return false;
}
let top = el.offsetTop;
let left = el.offsetLeft;
const width = el.offsetWidth;
const height = el.offsetHeight;
const vpSize = getViewportSize();
const scrollTop = getScrollPos();
const scrollLeft = getScrollPos(undefined, true);
while (el.offsetParent) {
el = el.offsetParent as any;
top += el.offsetTop;
left += el.offsetLeft;
}
// Convert legacy values
if (isNumber(options)) {
options = {offsetTop: options as number};
}
const opt: IsElementInViewportOptions = isUndefined(options) ? {} : options as any;
// Apply top offset
top += (isNumber(opt.offsetTop) ? opt.offsetTop : 0);
// Handle full collision
const of = opt.onlyFull;
// Limit Bottom
return top + (of ? height : 0) < vpSize.height + scrollTop &&
// Limit Right
left + (of ? width : 0) < vpSize.width + scrollLeft &&
// Limit Top
top + (of ? 0 : height) > scrollTop &&
// Limit left
left + (of ? 0 : width) > scrollLeft;
}