How to remove ',' from Date String-CodePudding

I have a simple output of a date that looks like the following:

May 16, 2022, 1:00 PM

what I want to do is to replace it with the following string:

May 16, 2022 at 1:00 PM

I found this regex: .replace(/,*$/, " at");

According to that answer, I should get my desired result but instead I receive the following:

May 20, 2022, 1:00 AM at

It simply appends at at the end of the string. Can I please get some help on how to tweak the regex? JavaScript is not my strongest language and regex even less.

CodePudding user response：

You need a way to match the second comma but not the first.

One way is to use a negative lookahead to prevent a match if there is another comma further along in the string.

const output  = "May 16, 2022, 1:00 PM";

console.log(output.replace(/,(?!.*,)/, " at"));

Your regex /,*$/ means match zero or more commas followed immediately by the end of the string - clearly that is not useful here.

CodePudding user response：

Assuming the string will never change, the comma you want to replace is always going to be the last one in the string. So you could write a function that splices then concatenates the strings around the index of the last comma, like so:

function format_date(s) {
  const i = s.lastIndexOf(',');
  return s.slice(0, i)   " at"   s.slice(i   1);
}

The regex you posted will not replace the last comma inside a string, but only the trailing commas at the very end of the string (even if there aren't any).

CodePudding user response：

Use split() and replace():

const output  = "May 16, 2022, 1:00 PM"
const wordReplace = output.split(" ")[2]
const result = output.replace(wordReplace, `${wordReplace.split(",")[0]} at`)
console.log(result)

CodePudding user response：

const regex = /(\d{4}), (\d :\d )/gm;

// Alternative syntax using RegExp constructor
// const regex = new RegExp('(\\d{4}), (\\d :\\d )', 'gm')

const str = `May 16, 2022, 1:00 PM`;
const subst = `$1 at $2`;

// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log(result);