2.0.0: Only audit nodes that have changed #8
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jul-sh
commented
Nov 29, 2019
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| this._mutationObserver = new window.MutationObserver(mutationRecords => { | ||
| mutationRecords.forEach(mutationRecord => { | ||
| this._auditNode(mutationRecord.target) | ||
| }) | ||
| }) |
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Audit each mutated node individually
jul-sh
commented
Nov 29, 2019
| if (!targetNode) { | ||
| throw new Error('AxeObserver.observe requires a targetNode') | ||
| } | ||
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| const scheduleAudit = debounce( | ||
| () => requestIdleCallback(() => this._auditTargetNode(targetNode)), |
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Once the debounced function fired, we also scheduled the whole node audit via requestIdleCallback. While the audit was started during an idle period, it would often take several hundred ms to run. Hence the requestIdleCallback wasn't that useful, since the work would continue way past the actual idle period.
In the new version, smaller chunks of work are used. They get executed for only as long as the idle period lasts.
jul-sh
commented
Nov 29, 2019
jul-sh
commented
Nov 29, 2019
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Previously agnostic-axe would audit the whole observed node (usually the document) if a part of it changed. For larger pages this would be quite an intense operation, so audits were debounced for performance.
This version now only audits the individual parts that have changed. Each node passed by the MutationObserver is audited individually. This means we have smaller chunks of work that better fit into the browsers idle period. In addition, less content has to be audited.
To make this happen, this adds the
AuditQueueclass, which keeps a queue of pending audits and executes them during idle periods. Debouncing options have been removed. Audits are run as soon as the browser has idle time.