It seems like the method has already been executed despite encountering an unexpected end of JSON input error

Question

It seems like the method has already been executed despite encountering an unexpected end of JSON input error

Currently, I am utilizing the etherscan API to retrieve logs for certain events. Although my JSON parsing method seems quite traditional, an error is being thrown stating "unexpected end of JSON".

function getEventHistory() {
    const topic0 = web3.utils.keccak256(config.event_string);
    document.getElementById("topic0").innerHTML = topic0;
    const qry = ("https://api.etherscan.io/api?module=logs&action=getLogs"+
                    "&fromBlock="+10338000+
                    "&toBlock="+"latest"+
                    "&address="+config.address+
                    "&topic0="+topic0+
                    "&apikey="+config.ether_api);
    console.log(qry)
    const request = new XMLHttpRequest()
    request.open("GET", qry);
    request.send();
    request.onreadystatechange=(e)=>{
        // document.getElementById("rLogsResp").innerHTML = request.responseText;
        parseResponse(request.responseText);
    }
}

function parseResponse(jsonString) {
    console.log("Converting string to jsonString: "+jsonString);
    const jsonObj = JSON.parse(jsonString)
    console.log("Full Response: "+jsonObj);

    var logs = []
    for (var i = 0; i < jsonObj.result.length; i++) {
        console.log("Element Number: "+i);
        var event = jsonObj.result[i];
        console.log("Index: "+event);
        const parsedEvent = new Event(event);
        logs.push(parsedEvent)
        console.log(parsedEvent);
    }
}

class Event {
    constructor(event) {;
        console.log("Parse address: "+event.address);
        this.address = web3.utils.toAscii(event.address);
        console.log("Parse topics: "+event.topics);
        this.topics = [web3.utils.toAscii(event.topics[0]), web3.utils.toAscii(event.topics[1]), web3.utils.toAscii(event.topics[2])];
        console.log("Parse data: "+event.data);
        this.data = web3.utils.toAscii(event.data);
        console.log("Parse blockNumber: "+event.blockNumber);
        this.blockNumber = web3.utils.toAscii(event.blockNumber);
        console.log("Parse timeStamp: "+event.timeStamp);
...

        
<p>Even though I'm relatively inexperienced with JavaScript, it seems like <code>onreadystatechange is being triggered multiple times as the issue arises on const jsonObj = JSON.parse(jsonString). Nonetheless, I do end up receiving the logs from the subsequent for loop.
If anyone can offer insight into what might be wrong and how to rectify it, that would be greatly appreciated!

javascript json request

Answer 1

Answer №1

Indeed, multiple calls to the onreadystatechange function do occur.

The documentation outlines the timing of these calls, and you can utilize the readyState attribute to determine the current status of the XML HTTP request:

https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/onreadystatechange

Answer 2

Indeed, multiple calls to the onreadystatechange function do occur.

The documentation outlines the timing of these calls, and you can utilize the readyState attribute to determine the current status of the XML HTTP request:

https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/onreadystatechange

It seems like the method has already been executed despite encountering an unexpected end of JSON input error

Answer №1

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