regex - JavaScript Regular Expression Match Return the Input as the First 2 Indexies -

i getting started regex in javascript (and in general) , have come across oddity can't seem find explanation using google.

without getting detail, using following expression:

/(^sw:\s?(-?\d{1,3}.\d{1,6})\sne:\s?(-?\d{1,3}.\d{1,6})$)/i 

which matching user input like:

sw: -27.990344 ne: 150.234562 

with following console.log output:

["sw: -27.345455 ne: 180.234567", "sw: -27.345455 ne: 180.234567", "-27.345455", "180.234567"]  0 "sw: -27.345455 ne: 180.234567"    1 "sw: -27.345455 ne: 180.234567"    2 "-27.345455"   3 "180.234567"  index 0 input "sw: -27.345455 ne: 180.234567" 

my question is: why index 0 , 1 returning user supplied input , actual data return index 2 , 3?

i assume relative expression, don't know enough sure not normal behaviour.

any appreciated.

index 0 complete match, capturing groups starting @ index 1.

the capturing groups numbered opening brackets, first opening bracket group 1, second opening bracket group 2, ...

you have brackets around complete expression, first capturing group. ==> outer brackets not needed, can remove them , groups start @ index 1.

for more information capturing groups can have @ /www.regular-expressions.info, resource regexes.