@atlaskit/editor-core/dist/es2019/utils/performance/getTimeSince.js

A package contains Atlassian editor core functionality

/**
 * Calculate the difference between performance.now() and the given startTime.
 * This allows for the timing to be overridable during tests.
 *
 * @param startTime DOMHighResTimeStamp
 * @returns DOMHighResTimeStamp
 */
export const getTimeSince = startTime => performance.now() - startTime;