const regex = /.*?id="(.*?)".*?time">(.*?)<\/.*?subject">\[(.*?)\].*?|.*$/gs;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('.*?id="(.*?)".*?time">(.*?)<\\\/.*?subject">\\[(.*?)\\].*?|.*$', 'gs')
const str = `<div class="list" id="1">
<div class="time">12:01 PM</div>
<div class="subject">[This is dummy Subject1] This is some dummy strings after subject</div>
<div/>
<div class="list" id="2">
<div class="time">12:01 PM</div>
<div class="subject">[This is dummy Subject2] This is some dummy strings after subject</div>
<div/>
<div class="list" id="3">
<div class="time">12:01 PM</div>
<div class="subject">[This is dummy Subject3] This is some dummy strings after subject</div>
<div/>`;
const subst = `$1|$2|$3\n`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions