| 1 | "use strict";
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| 2 |
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| 3 | module.exports = {
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| 4 | getRootMargin,
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| 5 | getIntersectionRatio
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| 6 | };
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| 7 |
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| 8 | function getRootMargin({rootMargin = ""} = {}) {
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| 9 | const [top, right, bottom, left] = rootMargin
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| 10 | .split(" ")
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| 11 | .map((num) => parseInt(num));
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| 12 |
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| 13 | return {
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| 14 | top: firstOf(top),
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| 15 | right: firstOf(right, top),
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| 16 | bottom: firstOf(bottom, top),
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| 17 | left: firstOf(left, right, top)
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| 18 | };
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| 19 | }
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| 20 |
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| 21 | function firstOf(...args) {
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| 22 | for (let i = 0; i < args.length; i++) {
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| 23 | if (args[i] !== undefined && !isNaN(args[i])) {
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| 24 | return args[i];
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| 25 | }
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| 26 | }
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| 27 |
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| 28 | return 0;
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| 29 | }
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| 30 |
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| 31 | function getIntersectionRatio(boundingClientRect, windowInnerHeight, rootMargin = {}) {
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| 32 | const {top, height, bottom = top + height} = boundingClientRect;
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| 33 | const {top: marginTop, bottom: marginBottom} = rootMargin;
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| 34 |
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| 35 | const topIntersection = -(marginTop || 0);
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| 36 | const bottomIntersection = windowInnerHeight + (marginBottom || 0);
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| 37 |
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| 38 | if (top < topIntersection) {
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| 39 | return Math.max((bottom - topIntersection) / height, 0);
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| 40 | }
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| 41 |
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| 42 | if (bottom > bottomIntersection) {
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| 43 | return Math.max((bottomIntersection - top) / height, 0);
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| 44 | }
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| 45 |
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| 46 | return 1;
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| 47 | }
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