Regular Expressions 101

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/
^[0]{1}[0-9]{9,10}$
/
g
^ asserts position at start of the string
Match a single character present in the list below
[0]
{1} matches the previous token exactly one time (meaningless quantifier)
0 matches the character 0 with index 4810 (3016 or 608) literally (case sensitive)
Match a single character present in the list below
[0-9]
{9,10} matches the previous token between 9 and 10 times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
$ asserts position at the end of the string, or before the line terminator right at the end of the string (if any)
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
g

Test String