# The lastIndex property in JavaScript regexes

A regular expression has the `lastIndex` property. It contains the position from which the next call of the `exec` method will start searching. That is, with each new method call, this property will change its value. Let's look at an example:

`let str = '12 34 56'; let reg = /\d+/g; console.log(reg.lastIndex); // initial value is 0 let res; while (res = reg.exec(str)) { console.log(res); // [12], [34], [56] console.log(reg.lastIndex); // 2, 5, 8 }`

The advantage of `lastIndex` is that it can be not only read, but also changed, starting the search from a given position. See an example:

`let str = '12 34 56'; let reg = /\d+/g; reg.lastIndex = 2; let res = reg.exec(str) console.log(res); // [34]`

Given the following string:

`let str = '12:37 15:48 17:59';`

Find in it all substrings with the time, starting from the fifth character.

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