performance.measure(name[, startMark[, endMark]])
在性能时间轴中创建新的 PerformanceMeasure
条目。
PerformanceMeasure
是 PerformanceEntry
的子类,其 performanceEntry.entryType
始终为 'measure'
,其 performanceEntry.duration
测量自 startMark
和 endMark
以来经过的毫秒数。
startMark
参数可以标识性能时间轴中的任何现有的 PerformanceMark
,或者可能标识由 PerformanceNodeTiming
类提供的任何时间戳属性。
如果命名的 startMark
不存在,则默认情况下将 startMark
设置为 timeOrigin
。
可选的 endMark
参数必须标识性能时间轴中的任何现有的 PerformanceMark
或 PerformanceNodeTiming
类提供的任何时间戳属性。
不传入参数则 endMark
为 performance.now()
,否则如果命名的 endMark
不存在,则抛出错误。
Creates a new PerformanceMeasure
entry in the Performance Timeline. A
PerformanceMeasure
is a subclass of PerformanceEntry
whose
performanceEntry.entryType
is always 'measure'
, and whose
performanceEntry.duration
measures the number of milliseconds elapsed since
startMark
and endMark
.
The startMark
argument may identify any existing PerformanceMark
in the
Performance Timeline, or may identify any of the timestamp properties
provided by the PerformanceNodeTiming
class. If the named startMark
does
not exist, then startMark
is set to timeOrigin
by default.
The optional endMark
argument must identify any existing PerformanceMark
in the Performance Timeline or any of the timestamp properties provided by the
PerformanceNodeTiming
class. endMark
will be performance.now()
if no parameter is passed, otherwise if the named endMark
does not exist, an
error will be thrown.