ReactJS toLowerCase is not a function

Question

I am doing a comparison by converting my text to lowercase and comparing its index to -1, in order to have some value to the particular field in ReactJS, but I am getting this error in JavaScript console:

Uncaught TypeError: props.filterText.toLowerCase is not a function

var props = this.props;
var rows = this.props.episodes
    .filter(function(episode){
        return episode.title.toLowerCase().indexOf(props.filterText.toLowerCase()) > -1;
    })
    .map(function(episode){
       return <EpisodeRow key={episode.title} episode={episode}/>
    });

Bogor

What value does props.filterText have? – Slaton

Is episode.title a String? try episode.title.toString().toLowerCase() or console.log its' value to the console. – Tondatone

This is a pretty straightforward error - props.filterText is not a string. Just do a console.log inside your filter loop of props.filterText and you'll see it's not a string. My guess is that it will be undefined – Lipolysis

@adam: would undefined cause a RefError "undefined has no property toLowerCase"... ? – Archaism

Probably a very minor performance issue as well - but why do .toLowerCase() in a loop every time if you don't have to? var filter = props.filterText.toLowerCase() outside your filter function and do indexOf(filter) inside your function. – Lipolysis

@Archaism - you're right, it's not undefined it's just something that's not a string. Could be a function, number, boolean, but not a string. – Lipolysis

Answer 1

Looks like Chris's comment is the correct answer:

If title is a string, use toString() before toLowerCase():

return episode.title.toString().toLowerCase().indexOf(props.filterText.toString().toLowerCase()) > -1;

Naphthol

In my particular case, this solution rendered the text as "[Object] [Object]". You shouldn't be guessing when coding in a strongly-typed language. – Calvary

Answer 2

I think I found the problem :)

props.filterText is undefined. => The filterText:"" must be declared in the state before putting in props

Implement

I had this problem again 2 times. – Jocose

Answer 3

I think Adam's answer from the comments is actually correct, and turned out to solve my problem :

.filter(function(episode){
    if(episode.title) {
        return episode.title.toLowerCase().indexOf(props.filterText.toLowerCase()) > -1;
    } else {
        return '';
    }
})

Calvary