I have a code that results undefined whenever I try fetch results into a variable

var data;
fetch('./js/samplejson.json')
    .then((res) => res.json())
    .then(output => {
        var data = output;
    } 
)
console.log(data);

How can I get a result of

[1, 2, 3]

inside data variable

I have a code that results undefined whenever I try fetch results into a variable

var data;
fetch('./js/samplejson.json')
    .then((res) => res.json())
    .then(output => {
        var data = output;
    } 
)
console.log(data);

How can I get a result of

[1, 2, 3]

inside data variable

• javascript
• json
• variables
• fetch
• put

• @MichaelGeary yup.thats true.he is declared the data at the top.like [1,2,3] earlier – zabusa Commented Jan 22, 2018 at 10:04

2 Answers 2

The fetch() call is asynchronous. It returns before the data es back from the server. When you try to access the data after the call, you're trying to access it before the server has responded.

You need to handle that data inside the callback, or in a function called from that callback. In other words, where you do var data = output;, don't do that. It won't help to remove the var so the code sets the global data variable as suggested in a ment. The problem isn't scope, it's timing. Process the output data right there inside the callback, or call another function and pass output to it.

You can get data from log here.

fetch('./js/samplejson.json')
    .then((res) => res.json())
    .then(output => {
        var data = output;
        console.log(data);
    } 
)