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23 lines
858 B
23 lines
858 B
import { union, without } from './utils/js_utils';
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export default class EnterLeaveCounter {
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constructor(isNodeInDocument) {
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this.entered = [];
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this.isNodeInDocument = isNodeInDocument;
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}
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enter(enteringNode) {
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const previousLength = this.entered.length;
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const isNodeEntered = (node) => this.isNodeInDocument(node) &&
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(!node.contains || node.contains(enteringNode));
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this.entered = union(this.entered.filter(isNodeEntered), [enteringNode]);
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return previousLength === 0 && this.entered.length > 0;
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}
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leave(leavingNode) {
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const previousLength = this.entered.length;
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this.entered = without(this.entered.filter(this.isNodeInDocument), leavingNode);
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return previousLength > 0 && this.entered.length === 0;
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}
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reset() {
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this.entered = [];
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}
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}
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