//replace all whitespaces with underscore
string.replace(new RegExp(/\s/g), '_');

//replace the word 'replace' with 'replaced'
string.replace(/replace/g, 'replaced');

string.replace(new RegExp(/\//g), '_');

string.replace(/replace/g, 'replaced');

return string.replace(new RegExp(/\//g), '_');

return string.replace(/replace/g, 'replaced');

Javascript string replace (all occurrences)

javascript, replace

JavaScript