这应该行得通：

str = str.replace(/\s*,\s*/g, ",");

var str = " I would like to know how to use RegExp    ,    string.match    and  string.replace";

console.log(
  str
);
console.log(
  str
  //Replace double space with single
  .replace(/  +/ig, ' ')
);
console.log(
  str
  //Replace double space with single
  .replace(/  +/ig, ' ')
  //Replace any amount of whitespace before or after a `,` to nothing
  .replace(/\s*,\s*/ig, ',')
);

使用RegEx：

\s*,\s*

DEMO

您可以尝试使用正则表达式，并获得有关https://regex101.com特性的详细文档
以下是.lau_对您的问题的解决方案：https://regex101.com/r/aT7pS5/1

我甚至会建议一个更好的，包括报价：

const text: string = 'Example "number-1" , something “ABC” , and something more.';

const regex: RegExp = /\s(?=[,"”])/g;
const resultat: string = text.replace(regex, '');

Example "number-1", something “ABC”, and something more.