const regex = /(?<!function )(?<!\/\/)print/g;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?<!function )(?<!\\\/\\\/)print', 'g')
const str = `<?php
// Description of file
...
print("Foobar");
// print("Foo");
//print("bar");
// Open and print file
function printtemplate(\$file) {
...
}
...
printtemplate(\$file);
...
?>`;
const subst = `//$0`;
// 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