javascript - Array.prototype.includes on Node js versions <= 4 - Stack Overflow

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I had written a Gruntfile, which makes heavy use of Array.prototype.includes() and similar functions. I have discovered I need to downgrade the version of node to version 4.4.5. Once I do this, I no long am able to use statements such as if ( myarray.includes(somevalue) ), and it will fail saying: >> TypeError: myarray.includes is not a function. When I look at the node documentation, it seems to be for the current version of node, so I'm not sure what's the alternative.

What is the equivalent of an array 'includes', in versions of node 4 and below? Also, are there other huge differences I'd need to be aware of? (Another I have found is no support for default params in a function declaration).

I had written a Gruntfile, which makes heavy use of Array.prototype.includes() and similar functions. I have discovered I need to downgrade the version of node to version 4.4.5. Once I do this, I no long am able to use statements such as if ( myarray.includes(somevalue) ), and it will fail saying: >> TypeError: myarray.includes is not a function. When I look at the node documentation, it seems to be for the current version of node, so I'm not sure what's the alternative.

What is the equivalent of an array 'includes', in versions of node 4 and below? Also, are there other huge differences I'd need to be aware of? (Another I have found is no support for default params in a function declaration).

• javascript
• arrays
• node.js
• gruntjs
• node-modules

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2 Answers 2

Sorted by: Reset to default 6

You can always just polyfill includes so that you can continue to use it. There's even an "official" polyfill here.

Anyway, barring that, the equivalent would be the indexOf method, which returns -1 if the item isn't found, or its index otherwise. So

array.includes(item);

can be replaced by

array.indexOf(item) !== -1;

The best way to handle this case would be to drop in a polyfill to allow you to run your code without having to modify it, since modifications could lead to bugs. The polyfill you are looking for can be found here. To use it, you need to run this code prior to trying to use .includes, usually wherever your application starts.

// https://tc39.github.io/ecma262/#sec-array.prototype.includes
if (!Array.prototype.includes) {
  Object.defineProperty(Array.prototype, 'includes', {
    value: function(searchElement, fromIndex) {

      if (this == null) {
        throw new TypeError('"this" is null or not defined');
      }

      // 1. Let O be ? ToObject(this value).
      var o = Object(this);

      // 2. Let len be ? ToLength(? Get(O, "length")).
      var len = o.length >>> 0;

      // 3. If len is 0, return false.
      if (len === 0) {
        return false;
      }

      // 4. Let n be ? ToInteger(fromIndex).
      //    (If fromIndex is undefined, this step produces the value 0.)
      var n = fromIndex | 0;

      // 5. If n ≥ 0, then
      //  a. Let k be n.
      // 6. Else n < 0,
      //  a. Let k be len + n.
      //  b. If k < 0, let k be 0.
      var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

      function sameValueZero(x, y) {
        return x === y || (typeof x === 'number' && typeof y === 'number' && isNaN(x) && isNaN(y));
      }

      // 7. Repeat, while k < len
      while (k < len) {
        // a. Let elementK be the result of ? Get(O, ! ToString(k)).
        // b. If SameValueZero(searchElement, elementK) is true, return true.
        if (sameValueZero(o[k], searchElement)) {
          return true;
        }
        // c. Increase k by 1. 
        k++;
      }

      // 8. Return false
      return false;
    }
  });
}

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