[рони]

rsaburov,

const removeKeyword = (str, keyword) => str.split(/\r?\n/).filter(a => !a.includes(keyword)).join('\n');
let str = `123 test
Здравствуй мир 123
123 test`;
let keyword = 'Здравствуй мир';
str = removeKeyword(str, keyword);
alert(str);