Remove leading zeros from time format

You can use this replacement:

var result = yourstr.replace(/^(?:00:)?0?/, '');

demo

or better:

var result = yourstr.replace(/^0(?:0:0?)?/, '');

demo

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To deal with Matt example (see comments), you can change the pattern to:

^[0:]+(?=\d[\d:]{3})

If you use 1 h instead of two you will not get the leading 0.

h:mm:ss