const regex = /^.*(\b\w+#\d+)[^{]*{.*{ *([^}]*?) *}.*$/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('^.*(\\b\\w+#\\d+)[^{]*{.*{ *([^}]*?) *}.*$', 'gm')
const str = `
net trunk trunk#1 { bandwidth 20000 cfg-mbr-count 2 id 0 interfaces { 2.1 2.2 } lacp enabled
net trunk trunk#2 { bandwidth 4000 cfg-mbr-count 2 id 0 interfaces { 1.1 1.2 1.3 1.4 } lacp enabled
net trunk chocolatesilk#314 { bandwidth 4000 cfg-mbr-count 2 id 0 interfaces { 3.14.15.92 65.35.89.79 } lacp enabled
net trunk edisthestandardtexteditor#237 { bandwidth 4000 cfg-mbr-count 2 id 0 interfaces { 101.100.105.116 116.101.120.116 } lacp enabled
`;
const subst = `$1 $2`;
// 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