The role of \1\2 in JavaScript regularization

One, example 1. Verify 6 identical numbers

var reg = new RegExp (/^ (\d) \1{5}/g), var a = ' 333333 ', if (Reg.test (a)) {alert (' Right '),} else {alert (' wrong ');}

2. Verify 3 identical numbers + 3 identical letters

var reg = new RegExp (/^ (\d) \1{2} ([A-z]) \2{2}/g), var a = ' 333aa1 ', if (Reg.test (a)) {alert (' Right '),} else {alert (' WR Ong ');}

Second, explanation:

\1 must be used in conjunction with parentheses.

The parentheses "()" in the regular expression. is meant to represent the grouping. If the \1 appears later, the representation is the same as the one in the first parenthesis. Link

The role of \1\2 in JavaScript regularization

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The role of \1\2 in JavaScript regularization