Change to RegExp

Question

How can I write this condition simpler using RegExp?

if (current === '+' || current === '-' || current === '*' || current === '/')

Answer 1

   if(/[+*/-]/.test(current)){
      //do something
     } 

Escape these charcters as they have special meaning in regular expression.

Answer 2

if current is always one character,

• regex

  if (/[+*/-]/.test(current))
  

• ES6, no regex

  if ('+*/-'.contains(current))
  

• non-ES6, no regex

  if ('+*/-'.indexOf(current) !== -1)
  

• non-ES6, no regex, short

  if (~'+*/-'.indexOf(current))
  

if not,

• regex

  if (/^[+*/-]$/.test(current))
  

• ES6, no regex

  if ([...'+*/-'].contains(current))
  

• non-ES6, no regex

  if (['+', '*', '/', '-'].indexOf(current) !== -1)
  

Answer 3

You use a character class and the test function of regular expressions:

if (/^[-+*/]$/.test(current)) {
    // ...
}

Note the ^ and $ assertions (beginning and end of input), so that "-+" won't match.

Example:

var rex = /^[-+*/]$/;
["p", "+", "-", "-+"].forEach(function(current) {
  console.log(current, rex.test(current));
});