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is-implemented.js 394 B

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  1. 'use strict';
  2. module.exports = function () {
  3. var map;
  4. if (typeof WeakMap !== 'function') return false;
  5. map = new WeakMap();
  6. if (typeof map.set !== 'function') return false;
  7. if (map.set({}, 1) !== map) return false;
  8. if (typeof map.clear !== 'function') return false;
  9. if (typeof map.delete !== 'function') return false;
  10. if (typeof map.has !== 'function') return false;
  11. return true;
  12. };