Question

77

Checking whether something is iterable

rated 0 times [ 83] [ 6] / answers: 1 / hits: 85621 / 11 Years ago, wed, september 18, 2013, 12:00:00

In the MDN docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of

The for...of construct is described to be able to iterate over "iterable" objects. But is there a good way of deciding whether an object is iterable?

I've tried to find common properties for arrays, iterators and generators, but have been unable to do so.

Aside from doing a for ... of in a try block and checking for type errors, is there a clean way of doing this?

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albert

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answered 11 Years ago leifw · Accepted Answer

The proper way to check for iterability is as follows:

function isIterable(obj) {

  // checks for null and undefined

  if (obj == null) {

    return false;

  }

  return typeof obj[Symbol.iterator] === 'function';

}

Why this works (iterable protocol in depth): https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Iteration_protocols

Since we are talking about for..of, I assume, we are in ES6 mindset.

Also, don't be surprised that this function returns true if obj is a string, as strings iterate over their characters.