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19

Is there a difference between d and d+?

rated 0 times [ 21] [ 2] / answers: 1 / hits: 22450 / 8 Years ago, wed, june 29, 2016, 12:00:00

https://www.freecodecamp.com/challenges/find-numbers-with-regular-expressions

I was doing a lesson in FCC, and they mentioned that the digit selector d finds one digit and adding a + (d+) in front of the selector allows it to search for more than one digit.

I experimented with it a bit, and noticed that its the g right after the expression that searches for every number, not the +. I tried using d+ without the g after the expression, and it only matched the first number in the string.

Basically, whether I use d or d+, as long as I have the g after the expression, It will find all of the numbers. So my question is, what is the difference between the two?

// Setup

  var testString = There are 3 cats but 4 dogs.;



  var expression = /d+/g;

  var digitCount = testString.match(expression).length;

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answered 8 Years ago anais · Accepted Answer

The g at the end means global, ie. that you want to search for all occurrences. Without it, you'll just get the first match.

d, as you know, means a single digit. You can add quantifiers to specify whether you want to match all the following, or a certain amount of digits afterwards.

d means a single digit

d+ means all sequential digits

So let's say we have a string like this:

123 456

7890123

/d/g will match [1,2,3,4,5,6,7,8,9,0,1,2,3]

/d/ will match 1

/d+/ will match 123

/d+/g will match [123,456,7890123]

You could also use /d{1,3}/g to say you want to match all occurrences where there are from 1 to 3 digits in a sequence.

Another common quantifier is the star symbol, which means 0 or more. For example /1d*/g would match all sequences of digits that start with 1, and have 0 or more digits after it.