JavaScript regex pattern concatenate with variable

Question

How to create regex pattern which is concatenate with variable, something like this:

var test ="52"; var re = new RegExp("/\b"+test+"\b/");  alert('51,52,53'.match(re)); 

Thanks

Answer 1

var re = new RegExp("/\b"+test+"\b/");  

\b in a string literal is a backspace character. When putting a regex in a string literal you need one more round of escaping:

var re = new RegExp("\\b"+test+"\\b");  

(You also don't need the // in this context.)

Answer 2

With ES2015 (aka ES6) you can use template literals when constructing RegExp:

let test = '53'  const regexp = new RegExp(`\\b${test}\\b`, 'gi') // showing how to pass optional flags  console.log('51, 52, 53, 54'.match(regexp))