ent.querySelectorAll("[id]")).map((e) => e.id);
    
    const set = new Set(array);
    console.assert(set.size === array.length);
    

##  Specifications

Specification  
---  
[ ECMAScript Language Specification  
#  sec-set-objects  ](https://tc39.es/ecma262/multipage/keyed-
collections.html#sec-set-objects)  
  
##  Browser compatibility

BCD tables only load in the browser  with JavaScript enabled. Enable
JavaScript to view data.

##  See also

  * [ Polyfill of ` Set ` in ` core-js ` ](https://github.com/zloirock/core-js#set)
  * [ ` Map ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map)
  * [ ` WeakMap ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap)
  * [ ` WeakSet ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet)

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