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getBackgroundColor.ts
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getBackgroundColor.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: 2019.08.01 at 18:23
*/
import {isBrowser} from '../Environment/isBrowser';
import {isNull} from '../Types/isNull';
import {isObject} from '../Types/isObject';
import {isUndefined} from '../Types/isUndefined';
import type {RgbColor} from './Color.interfaces';
import {rgbStringToRgbColor} from './rgbStringToRgbColor';
/**
* Traverses the dom upwards, beginning by the given element and extracts their background color.
* If the background color is transparent it will be ignored and the search continues.
* The traversing stops as soon as either the HTML node is reached or a background color was found.
*
* If a color was found, the rgb value will be returned, if no color was found
* or it was completely transparent NULL is returned
* @param el
*/
export function getBackgroundColor(el: HTMLElement): RgbColor | null
{
if (!isBrowser()) {
return null;
}
if (!isObject(el)) {
return null;
}
let backgroundColor = null;
while (el) {
const backgroundColorLocal = window.getComputedStyle(el).backgroundColor;
if (backgroundColorLocal === null) {
break;
}
const rgba = backgroundColorLocal.match(/^rgba?\((\d+|0),\s*(\d+|0),\s*(\d+|0)(?:,\s*(\d+|0))?\)$/);
if (!isNull(rgba) && (isUndefined(rgba[4]) || rgba[4] !== '0')) {
backgroundColor = rgbStringToRgbColor(backgroundColorLocal);
}
if (el.tagName === 'HTML' || !isNull(backgroundColor) || !el.parentElement) {
break;
}
el = el.parentElement;
}
if (isNull(backgroundColor)) {
return null;
}
return backgroundColor;
}