Ethereum: Why on printing I get value of null from API call in Loop

Here is an example of an article based on your request:

Ethereum: Why a “null” value popped up during a looping API call

Given that cryptocurrency prices fluctuate rapidly, it can be difficult for developers to work with APIs that provide real-time data. One such API is the Ethereum TradingView API, which provides access to various financial markets, including Bitcoin (BTC) on the USDT pair.

However, when trying to retrieve price data using APIs such as “getPriceAction” and “getRSI”, a “null” value would unexpectedly pop up in some cases. This phenomenon left developers wondering why this is happening.

The problem

The problem lies in how we handle looping API responses. When you try to iterate through an array (COIN LIST) of crypto coins using “for” loops or other iteration constructs, each element can be either a value or null. In our case, it seems that the getPriceAction and getRSI functions return null values ​​for some API calls.

Deciphering the Code

To understand why this is happening, let’s break down the code:

const COIN_LIST = [
'BTCUSDT',
//...
];
for (leave coin from COIN_LIST) {
const price = getPriceAction(coin);
const rsi = getRSI(price);
console.log(DATA); // This line will print "null" in some cases
if (!price) {
// Handle null here
}
}

In this snippet, we loop through each element of “COIN_LIST” and call the “getPriceAction” and “getRSI” functions to retrieve the price data. The console.log(DATA) statement is only executed when a non-null value is retrieved from these functions.

The Solution

To solve this problem, you can add null checks before logging the data to the console:

const COIN_LIST = [
'BTCUSDT',
//...
];
for (leave the coin in COIN_LIST) {
const price = getPriceAction(coin);
const rsi = getRSI(price);
if (!price) {
continue; // Skip this iteration and move on to the next element
}
console.log(DATA); // This line will print the correct data
if (DATA === null || DATA !== 'null') {
// Handle unexpected values ​​here
}
}

By adding these checks, you can prevent “console.log(null)” statements from appearing in your logs. Instead, the loop will move on to the next iteration and continue processing the rest of the array.

Additional Tips

To further improve the robustness of your code:

• Use optional chaining

  : To avoid null checks, use optional chaining (?.) instead of direct null checks.

const price = getPriceAction(coin).then((data) => data.price);

• Handle API Errors: Don’t forget to handle potential errors that may occur during API calls, such as network issues or server downtime.

• Consider Caching Results: If you are working with large datasets, consider caching the retrieved price and RSI values ​​to avoid unnecessary API calls.

By following these tips, you can write more efficient and reliable code that handles null values ​​in loops without encountering errors.