The shape of space: JavaScript - Simple parser for variables embedded on strings

Used for parsing variables embedded on strings. To get local variables defined inside constant strings as a way to put dynamic content like app name and version inside string translations.

Example:

Original string:
${owner} amount is ${currency} ${value}. Sharon has ${currency} ${value}. x.y = ${x.y}

Parsed string:
Sharon amount is US$ 12,345.00. Sharon has US$ 12,345.00. x.y = 5

<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
</head>
<body>
  <script type="text/javascript">
    function Evaluator() {
    }

    Evaluator.prototype.matches = [];

    Evaluator.prototype.patterVarName = "[a-zA-Z_]+[_a-zA-Z0-9.]*";

    Evaluator.prototype.regex = new RegExp("\\${(" +
                                           Evaluator.prototype.patterVarName +
                                           ")}", "mg");

    Evaluator.prototype.reset = function() {
      for (var item in this.matches) {
        delete this.matches[item];
      }
    };

    Evaluator.prototype.collect = function(str) {
      this.reset();

      var match;

      while (match = this.regex.exec(str)) {
        try {
          this.matches[match[1]] = eval(match[1]);
        }
        catch (e) {
          console.log('Error: ' + e.message);
        }
      }
    };

    Evaluator.prototype.parse = function(str) {
      this.collect(str);

      for (var item in this.matches) {
        while (this.regex.test(str)) {
          str = str.replace('${' + item + '}', this.matches[item]);
        }
      }

      return str;
    };

    // Use

    var evaluator = new Evaluator();

    var owner = 'Sharon';
    var currency = 'US$';
    var value = '12,345.00';
    var x = {
      y: 5
    };

    var str = '${owner} amount is ${currency} ${value}. ' +
              'Sharon has ${currency} ${value} <br/>x.y = ${x.y}';

    document.write('<br/>Original string: <strong>' + str + '</strong><br/>');

    // Parse string

    str = evaluator.parse(str);

    document.write('Parsed string: <strong>' + str + '</strong><br/>');

    // Print variables in cache

    document.write('<br/>Variables:<br/>');

    for (var item in evaluator.matches) {
      document.write('- ' + item + ' = ' + evaluator.matches[item] + '<br/>');
    }
  </script>
</body>
</html>

The shape of space

Pages

Wednesday, August 14, 2013

JavaScript - Simple parser for variables embedded on strings

No comments:

Blog Archive

Links