I'm trying to insert dash into numbers but it is so hard to me... What I want to do is that insert dash into after 3 and 4 digits, for example,
replacing 123123412345 to 123-1234-12345.
The additional condition is that I replace it in input element. So I replace the number for every input event, i.e., I need to replace like
1 to 1
12 to 12
123 to 123
1231 to 123-1
...
1231234 to 123-1234
12312341 to 123-1234-1
...
123123412345 to 123-1234-12345
How can I do this using regex ??
You may try this regex:
(?<=^\d{3}|^\d{7})(?=\d)
-
Check the proof
const list = [
1,
12,
123,
1231,
1231234,
12312341,
123123412345
];
const regex = /(?<=^\d{3}|^\d{7})(?=\d)/g;
const result = list.map(e => regex[Symbol.replace](e, '-'));
console.log(result);Suppose it needs to split the first 3 next 4 digits only, it can be done with following regexp replacement
str.replace(/((?<!\d)\d{3}(?!\b)|(?<=^\d{3})\d{4}(?!\b))/g, '$1-')
Input string has to be all digits
document.getElementById('input').addEventListener('keyup', (e) => {
e.target.value = e.target.value.split('-').join('').replace(/((?<!\d)\d{3}(?!\b)|(?<=^\d{3})\d{4}(?!\b))/g, '$1-');
});
['1', '12', '123', '1231', '12312', '123123', '1231234', '12312341', '123123412', '1231234123', '12312341234', '123123412345']
.forEach(t => console.log(t.replace(/((?<!\d)\d{3}(?!\b)|(?<=^\d{3})\d{4}(?!\b))/g, '$1-')));<input id="input" type="text" size="20">