javascript - Object.fromEntries only available on iOS? (react native - NOT WEB) - Stack Overflow

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The title is pretty self explanatory but still, consider this sample code:

import * as React from 'react';
import { Text, View, StyleSheet } from 'react-native';
import { Constants } from 'expo';


export default class App extends React.Component {
  render() {
    return ( 
      <Text>
         {Object.fromEntries("test")}
      </Text>
    );
  }
}

Check it out on Expo Snacks

By opening it on an Android device, I get the error that the fromEntries function does not exist on Object:

But on iOS, it does exist:

(bad parameter supplied to it, but it exists, nevertheless)

So what's happening here? Aren't JS engines supposed to be identical between the 2 platforms? What other known discrepancies like these exist?

The title is pretty self explanatory but still, consider this sample code:

import * as React from 'react';
import { Text, View, StyleSheet } from 'react-native';
import { Constants } from 'expo';


export default class App extends React.Component {
  render() {
    return ( 
      <Text>
         {Object.fromEntries("test")}
      </Text>
    );
  }
}

Check it out on Expo Snacks

By opening it on an Android device, I get the error that the fromEntries function does not exist on Object:

But on iOS, it does exist:

(bad parameter supplied to it, but it exists, nevertheless)

So what's happening here? Aren't JS engines supposed to be identical between the 2 platforms? What other known discrepancies like these exist?

• javascript
• react-native
• object
• ecmascript-6
• expo

Share Improve this question Follow edited May 31, 2019 at 10:27 iuliu asked May 30, 2019 at 13:50 iuliuiuliu 7,16588 gold badges5151 silver badges7272 bronze badges 4

• Just to add browsers are by no-means the same. They all have varying JS engines, rendering engines etc etc. They all have their own priorities on implementing the spec and their own agenda on their preferred version of the spec. caniuse is a good resource for browser pat. – ste2425 Commented May 30, 2019 at 13:55
• Check the official spec-pliant polyfill: github./es-shims/Object.fromEntries – Christian C. Salvadó Commented May 30, 2019 at 13:59
• it just depends what javascript engine is used in the particular OS, some newer Android version support this, some don´t – CampSafari Commented May 30, 2019 at 21:37
• This question is about REACT-NATIVE guys, what browsers? What Android version? The engine is shipped with the app itself.. – iuliu Commented May 31, 2019 at 10:26

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 6

Most likely you have an old or not-fully-supported engine (check the docs). You can make an ES6 polyfill like this:

Object.fromEntries = Object.fromEntries || arr => arr.reduce((acc, [k, v]) => (acc[k] = v, acc), {});

Or an ES5 polyfill like this:

Object.fromEntries = Object.fromEntries || function(arr) {
    return arr.reduce(function(acc, curr) {
        acc[curr[0]] = curr[1];
        return acc;
    }, {});
};

just add the babel preset to your babel config: https://www.npmjs./package/babel-plugin-transform-object-from-entries

Functions like .flat(), Object.fromEntries, and some new ones are not yet supported by most browsers and Javascript engines. Which means we might see it being supported in the next update of android or iOS Javascript engines. support chart

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