React Native, For Loop shows only the first Array Element

Question

I have this function which supposed to loop through 20 elements of (smn) Array to show the elements that meets the IF condition, with this code I got only the first array elements:

    renderSMN() {
    const smn = ['fb', 'twt', 'snp', 'ins', 'ytu', 'lnk', 'tik', 'beh', 'pin', 'tmp', 'www', 'eml', 'wap', 'msg', 'tlg', 'lin', 'wch', 'skp', 'snd', 'oth'];
    for (let i = 0; i < 20; i++) {
        //alert(this.state.data.smu_+smn[i]);
        alert(i);
        if (this.state.data.smu_+smn[i] != "") {
            return (
                <View style={{ margin: 5 }}>
                    <TouchableOpacity onPress={() => {
                        this.props.navigation.navigate('Result', { postId: item.uid, otherParam: 'Pass whatever you want here', });
                    }}>
                        <Image source={{ uri: 'http://localhost/rest/smn/' + smn[i] + '.png' }} style={{ width: 100, height: 100, right: 0, }} />
                    </TouchableOpacity>
                <Text>{i}</Text>
                </View>
            );
        }

This how I get the Data from JSON file:

        fetch('http://localhost/rest/api/single_read.php/?id=' + postId, {
        method: 'GET'
    })
        .then((response) => response.json())
        .then((responseJson) => {
            console.log(responseJson);
            this.setState({
                data: responseJson
            })
        })
        .catch((error) => {
            console.error(error);
        });

Ivan Rubinson · Accepted Answer · 2020-08-15 19:34:28Z

1

Looks like you're exiting the loop early by returning the JSX on the first smn that matches the condition. What you may want to do instead is to return an array of JSXes, some of them being falsy. You can do this by maping the smns to JSX. Note that when working with arrays of JSX, it's recommended to explicitly pass a key prop to each array element's root element.

renderSMN() {
    const smn = ['fb', 'twt', 'snp', 'ins', 'ytu', 'lnk', 'tik', 'beh', 'pin', 'tmp', 'www', 'eml', 'wap', 'msg', 'tlg', 'lin', 'wch', 'skp', 'snd', 'oth'];
    return smn.map((s, i) => {
        alert(i);
        if (this.state.data.smu_+s != "") {
            return (
                <View style={{ margin: 5 }} key={i}>
                    <TouchableOpacity
                        onPress={() => {
                        this.props.navigation.navigate('Result', { postId: item.uid, otherParam: 'Pass whatever you want here', });
                        }}
                    >
                        <Image source={{ uri: 'http://localhost/rest/smn/' + s + '.png' }} style={{ width: 100, height: 100, right: 0, }} />
                    </TouchableOpacity>
                    <Text>{i}</Text>
                </View>
            );
        }
    });
}

Note that if the condition doesn't hold, the function returns undefined implicitly, which is falsy.

answered Aug 15, 2020 at 19:34

Ivan Rubinson

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3 Comments

HowardJohn Over a year ago

I use this.state.data.smu_nam to show to JSON item (Name) in render but it does not work in the Function that I made.

Ivan Rubinson Over a year ago

I don't understand your question @HowardJohn

HowardJohn Over a year ago

I've used this.state.data.smu_nam to display data from JSON, it works fine inside <View> , but not else where.

lkroneman · Accepted Answer · 2020-08-15 19:33:10Z

0

In the first iteration you return from the renderSMN without continuing the loop.

I'd advise doing something like.

return smn.map(smnItem => {
    if(this.state.data.smu_+smnItem !== '') {
        return (...)
    } 

    return null;
});

instead of the for loop. Which allows to to still use the return keyword

You'd want to replace instances of smn[i] with smnItem

answered Aug 15, 2020 at 19:33

lkroneman

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