Pattern matching to extract multiple numbers within a string

Question

Pattern matching to extract multiple numbers within a string

I need help extracting numbers from a string like:

There are 1,000 people in those 3 towns.

I want to create an array like

["1,000", "3"]

.

I found a number matching Regex from Justin in this question

^[+-]?(\d*|\d{1,3}(,\d{3})*)(\.\d+)?\b$

Although it works for checking if it is a number, it needs modification to work on sentences. Specifically, the removal of "start" and "end" markers (^ and $).

See the regex patterns at: regex101 with start/end defined regex101 without start/end defined

Removing the start and end definitions results in unnecessary 0-length matches, but it also splits numbers with commas in them.

How can I modify the regex (or create a new one) to successfully extract numbers from sentences, including those with commas?

An added challenge would be avoiding the occurrence of 0 length matches.

javascript regex

Answer 1

Answer №1

If you're open to considering different groups like 1,00,000 (which is common in some regions), then the expression /-?\d(?:[,\d]*\.\d+|[,\d]*)/g should work for you. I've tried simplifying it further, but it seems that when I attempt to do so, the example "333.33" gets split into "333" and "33" as separate numbers. Using the previous expression keeps it together.

Here's a live example:

const str = "There are 10,000 people in those 3 towns. That's 3,333.33 people per town, roughly. Which is about -67.33 from last year.";
const rex = /-?\d(?:[,\d]*\.\d+|[,\d]*)/g;
let match;
while ((match = rex.exec(str)) !== null) {
    console.log(match[0]);
}

Breaking down /\d(?:[,\d]*\.\d+|[,\d]*)/g:

-? - an optional minus sign (x15 pointed this out in their answer!)
\d - a digit
(?:...|...) - a non-capturing group with an alternation between
- [,\d]*\.\d+ - zero or more commas and digits followed by a decimal point and one or more digits, e.g., 3,333.33; or
- [,\d]* - zero or more commas and digits

The first option will match greedily and use the second alternative if there is no decimal point.

Answer 2

If you're open to considering different groups like 1,00,000 (which is common in some regions), then the expression /-?\d(?:[,\d]*\.\d+|[,\d]*)/g should work for you. I've tried simplifying it further, but it seems that when I attempt to do so, the example "333.33" gets split into "333" and "33" as separate numbers. Using the previous expression keeps it together.

Here's a live example:

const str = "There are 10,000 people in those 3 towns. That's 3,333.33 people per town, roughly. Which is about -67.33 from last year.";
const rex = /-?\d(?:[,\d]*\.\d+|[,\d]*)/g;
let match;
while ((match = rex.exec(str)) !== null) {
    console.log(match[0]);
}

Breaking down /\d(?:[,\d]*\.\d+|[,\d]*)/g:

-? - an optional minus sign (x15 pointed this out in their answer!)
\d - a digit
(?:...|...) - a non-capturing group with an alternation between
- [,\d]*\.\d+ - zero or more commas and digits followed by a decimal point and one or more digits, e.g., 3,333.33; or
- [,\d]* - zero or more commas and digits

The first option will match greedily and use the second alternative if there is no decimal point.

Answer 3

Answer №2

To take a different approach, one option is to separate the string by spaces and then check if each part can be converted into a number,

const extractNumbers = str => str.split(/\s+/)
                                .filter(part => part && parseFloat(part.replace(/[.,]/g, '')))


console.log(extractNumbers('There are 1,000 people in those 3 towns. More numbers -23.012 1,00,000,00'))

Answer 4

To take a different approach, one option is to separate the string by spaces and then check if each part can be converted into a number,

const extractNumbers = str => str.split(/\s+/)
                                .filter(part => part && parseFloat(part.replace(/[.,]/g, '')))


console.log(extractNumbers('There are 1,000 people in those 3 towns. More numbers -23.012 1,00,000,00'))

Answer 5

Answer №3

If you're looking to find both integer and decimal numbers with optional commas in the whole part but not in the decimal part, you can use this regular expression:

/[+-]?(?:(?:\d(?:,(?=\d))?)+(?:\.\d*)?|\.\d+)/

https://regex101.com/r/yOuBPx/1

Although the sample input provided may not cover all boundary conditions handled by this regex, it's best to experiment with different cases to see its full effect.

Answer 6

If you're looking to find both integer and decimal numbers with optional commas in the whole part but not in the decimal part, you can use this regular expression:

/[+-]?(?:(?:\d(?:,(?=\d))?)+(?:\.\d*)?|\.\d+)/

https://regex101.com/r/yOuBPx/1

Although the sample input provided may not cover all boundary conditions handled by this regex, it's best to experiment with different cases to see its full effect.

Pattern matching to extract multiple numbers within a string

How can I modify the regex (or create a new one) to successfully extract numbers from sentences, including those with commas?

Answer №1

Answer №2

Answer №3

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