displaying a result in render from a function in REACTJS

Question

I want to render the text 'Results!' and the name of the largestLikeResult from my getLargest() function.

    getLargest() { 
        var largestLikeResult = null
        var largerstLikeNum= 0 
        if(this.props.results!=null){
            //.map goes through every result
            this.props.results.map(i=> {
                console.log(i.name)
                this.state.resultsRef.child(this.replaceAll("."," ",i.name)).once('value',function(snapshot) {
                if(largerstLikeNum<snapshot.val().right)
                {   
                    console.log("new largest in town")
                    largerstLikeNum = snapshot.val().right 
                    largestLikeResult= i.name 
                    console.log(largestLikeResult)
                }
                }) 
            })
            return (
                <div>
                {largestLikeResult}
                </div>
                )


        }
        else {
            return null
        }
    }

    render(){ 
        return (
            <div>
            Results! 
            <h1>{this.getLargest()}</h1>
            </div>  
        ) 
    }  
}
export default DisplayResults

Currently, only Results! shows up on page and the name of the largestLikeResult shows up in the console, not page. Any quick changes I can add to render() to show the value of largestLikeResult?

Thanks in advance!

Jee Mok · Accepted Answer · 2018-06-26 23:39:25Z

For a quick change, I think if you change from map to forEach it will work fine:

this.props.results.forEach(i => {

But I'd suggest to refactor getLargest() function into something similar to this:

getLargest() { 
    let largerstLikeNum = 0; 
    const { results } = this.props;
    const { resultsRef } = this.state;

    // Always return early
    if (!results || !Array.isArray(results)) {
      return null;
    }

    return (
      <div>
        {
          results.map(i => {
              return resultsRef.child(this.replaceAll('.', ' ', i.name)).once('value', snapshot => {
                if (largerstLikeNum < snapshot.val().right) {   
                    console.log('new largest in town');
                    largerstLikeNum = snapshot.val().right ;
                    return (
                      <div>{i.name}</div>
                    );
                }
                return null;
              }) 
          })
        }
      </div>
    );
}

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