Filter API Data Based on Array Of Strings

Question

I'm trying to filter out data from fetch of an external API (CoinMarketCap) in React.

I only want the data for a specific set of tickers, but after numerous attempts I can't seem to get it to work correctly. I feel like this should be an easy fix, but can't seem to figure it out.

getData = () => {
      const tickers = ["btc", "xrp", "eth", "ltc", "bch", "etc", "str", "xmr", "nxt", "zec", "rep", "dash"];
      fetch(`https://api.coinmarketcap.com/v1/ticker`)
      .then(res => res.json())
      .then(data => data.filter(d => tickers.includes(d.symbol)))
      .then(results => console.log(results)
    )

But it's logging out an empty array. Any ideas?

If you are receiving data from the above API, then your array#filter callback should be filter(d => tickers.includes(d.symbol.toLowerCase())) — Hassan Imam
– Hassan Imam, Commented Feb 21, 2018 at 3:13

Emad Emami · Accepted Answer · 2018-02-21 03:57:26Z

1

each then() needs a Promise or any thenable function. problem is that Array.prototype.filter() is not a promise and not resolving anything (it's not async function). you should write this:

getData = () => {
      const tickers = ["btc", "xrp", "eth", "ltc", "bch", "etc", "str", "xmr", "nxt", "zec", "rep", "dash"];
      fetch(`https://api.coinmarketcap.com/v1/ticker`)
      .then(res => res.json())
      .then(data => console.log(data.filter(d => tickers.includes(d.symbol))))
    )

answered Feb 21, 2018 at 3:57

Emad Emami

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Comments

Leomar Amiel · Accepted Answer · 2018-02-21 04:07:27Z

0

If you were getting the data from fetch, add toLowerCase() to the d.symbol

tickers.include(d.symbol.toLowerCase()

answered Feb 21, 2018 at 4:07

Leomar Amiel

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Comments

John Rogerson · Accepted Answer · 2018-02-21 17:27:21Z

0

Turns out this was a CORS issue. I had to move the fetch to my backend and called from REACT component. Working fine now. Thanks.

answered Feb 21, 2018 at 17:27

John Rogerson

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