Source: interpolation.js

  1. const errors = require('./errors');
  3. /**
  4.  * Regular Expression to match placeholders.
  5.  * @type {RegExp}
  6.  * @private
  7.  */
  8. const PLACEHOLDER = new RegExp(/%\(([\w-]+)\)s/);
  10. /**
  11.  * Maximum recursion depth for parseValue
  12.  * @type {number}
  13.  */
  14. const MAXIMUM_INTERPOLATION_DEPTH = 50;
  16. /**
  17.  * Recursively parses a string and replaces the placeholder ( %(key)s )
  18.  * with the value the key points to.
  19.  * @param {ParserConfig} parser - Parser Config Object
  20.  * @param {string} section - Section Name
  21.  * @param {string} key - Key Name
  22.  */
  23. function interpolate(parser, section, key) {
  24.     return interpolateRecurse(parser, section, key, 1);
  25. }
  27. /**
  28.  * Interpolate Recurse
  29.  * @param parser
  30.  * @param section
  31.  * @param key
  32.  * @param depth
  33.  * @private
  34.  */
  35. function interpolateRecurse(parser, section, key, depth) {
  36.     let value = parser.get(section, key, true);
  37.     if(depth > MAXIMUM_INTERPOLATION_DEPTH){
  38.         throw new errors.MaximumInterpolationDepthError(section, key, value, MAXIMUM_INTERPOLATION_DEPTH);
  39.     }
  40.     let res = PLACEHOLDER.exec(value);
  41.     while(res !== null){
  42.         const placeholder = res[1];
  43.         const rep = interpolateRecurse(parser, section, placeholder, depth + 1);
  44.         // replace %(key)s with the returned value next
  45.         value = value.substr(0, res.index) + rep +
  46.             value.substr(res.index + res[0].length);
  47.         // get next placeholder
  48.         res = PLACEHOLDER.exec(value);
  49.     }
  50.     return value;
  51. }
  53. module.exports = {
  54.     interpolate,
  55.     MAXIMUM_INTERPOLATION_DEPTH
  56. };