React-native-reanimated: Is cond() work unexpected?

[erkangozukucuk]

Description

When run below code i get this output:

render home
equal values
not equal values

What am i missing?

Code

// code goes here
import React, {useEffect} from 'react';
import {View} from 'react-native';
import {cond, eq, Value} from 'react-native-reanimated';

const val = new Value(10);
const val2 = new Value(5);

const Home = () => {
  useEffect(() => {
    cond(
      eq(val, val2),
      console.log('equal values'),
      console.log('not equal values'),
    );
  }, []);
  console.log('render home');

  return <View style={{flex: 1}}></View>;
};
export default Home;

Package versions

• React:16.11.0
• React Native:0.62.2
• React Native Reanimated:1.9.0

[jakub-gonet]

Hi @erkangozukucuk,

it seems you're mixing reanimated nodes with JS code, so the result may be surprising.

It works as expected, because you use cond node (which is a function from JS side), so JS evaluates arguments:

• eq evaluates to eq node
• both console.logs evaluates to undefined and prints text on the console as a side effect

Try it yourself by adding:

const some_function = () => {
  console.log('eq');
  return 5;
};

and changing nodes to:

cond(eq(val, val2), some_function(), console.log('not equal values'));

If you have any further concerns don't hesitate to reopen.