Changing matching quotes

quotes.js

var fs = require('fs');
var esprima = require('esprima');
var input = process.argv[2];
var content = fs.readFileSync(input, 'utf-8');
var tokens = esprima.parse(content, {
  tokens: true,
  range: true
}).tokens;

function convert(literal) {
  var result = literal.substring(1, literal.length - 1);
  result = result.replace(/'/g, '\\\'');
  return '\'' + result + '\'';
}

tokens.forEach(function(token) {
  var str;
  if (token.type === 'String' && token.value[0] !== '\'') {
    str = convert(token.value);
    content = content.substring(0, token.range[0]) + str +
      content.substring(token.range[1], content.length);
  }
});

fs.writeFileSync(input, content);