javascript - Parsing JSON File from XMLHttpRequest - Stack Overflow

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I would like to use data within a JSON file which I get by using the XMLHttpRequest. I already checked that I recieve the file.

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("demo").innerHTML = this.responseText;
    }
};
var obj = xhttp.open("GET", "../data/data.json", true);
xhttp.send();
var obj1 = JSON.parse(obj);
a0 = obj1.a0;

This is my JSON file.

{"a0":2, "a1": -2.356, "a2": 4.712}

I can't find the mistake I am doing here. Can you help?

I would like to use data within a JSON file which I get by using the XMLHttpRequest. I already checked that I recieve the file.

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("demo").innerHTML = this.responseText;
    }
};
var obj = xhttp.open("GET", "../data/data.json", true);
xhttp.send();
var obj1 = JSON.parse(obj);
a0 = obj1.a0;

This is my JSON file.

{"a0":2, "a1": -2.356, "a2": 4.712}

I can't find the mistake I am doing here. Can you help?

• javascript
• json
• ajax
• xmlhttprequest

Share Improve this question Follow edited Mar 1, 2017 at 15:07 Yaman Jain 1,2451111 silver badges1717 bronze badges asked Mar 1, 2017 at 13:49 DenisDenis 2911 gold badge22 silver badges99 bronze badges 1

• There is a pretty obvious difference between innerHTML = this.responseText; and obj = xhttp.open("GET", "../data/data.json", true); – Quentin Commented Mar 1, 2017 at 13:54

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2 Answers 2

Sorted by: Reset to default 2

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("demo").innerHTML = this.responseText;
        var obj=this.responseText;
        var obj1 = JSON.parse(obj);
        a0 = obj1.a0;
    }
};
xhttp.open("GET", "../data/data.json", true);
xhttp.send();

You need to get the response text inside the xhttp response.

onreadystatechange is a callback. That means that it's called asynchonously when the request ended. SO a part of your code is misplaced. Here the correction:

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("demo").innerHTML = this.responseText;
        var obj1 = JSON.parse(this.responseText);
        var a0 = obj1.a0;
    }
};
xhttp.open("GET", "../data/data.json", true);
xhttp.send();

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