How to make javascript fetch synchronous?

Question

I'm using fetch to get data json from an api. Works fine but I have to use it repeatedly for various calls, thus it needs to be synchronous or else I need some way to update the interface when the fetch completes for each component.

function fetchOHLC(yUrl){
    fetch(yUrl)
    .then(response => response.json())
    .then(function(response) {
                alert(JSON.stringify(response.query));

            var t = response.created;
            var o = response.open;
            var h = response.high;
            var l = response.low;
            var c = response.close;

        return {t,o,h,l,c};

    })
    .catch(function(error) {
        console.log(error);
    });    
}

var fetchData = fetchOHLC(yUrl);
alert(fetchData); // empty ?

Is there any other way to achieve it other than using fetch? (I don't want to use jquery preferrably).

Thanks

Edit

The question is about fetch-api, not ajax, not jquery, so please stop marking it as duplicate of those questions without reading it properly. And if you still feel compelled to do so, please stop linking it to decade old questions and answers, a lot changes in a decade.

Answer 1

If you came here because you dropped "how to make javascript fetch synchronous" into a search engine:

That doesn't make much sense. Performing network operations is not something which requires CPU work, thus blocking it during a fetch(...) makes little sense. Instead, properly work with asynchrony as shown in the duplicates linked above.

Original answer for the question:

You want your fetch function to return sth:

function fetchOHLC(yUrl){
    return fetch(yUrl)
    .then(response => response.json())
    .then(function(response) {
            alert(JSON.stringify(response.query));

        var t = response.created;
        var o = response.open;
        var h = response.high;
        var l = response.low;
        var c = response.close;

    return {t,o,h,l,c};

    })
    .catch(function(error) {
        console.log(error);
    });    
}

Now fetchData contains a promise, which can be easily used:

var fetchData = fetchOHLC(yUrl);
fetchData.then(alert); //not empty ! its {t,o,h,l,c}

---

If you want some fancy ES7, you could rewrite the whole thing like this:

async function fetchOHLC(yUrl) {
  try {
    const res = await ( await fetch(yUrl) ).json();
    alert(JSON.stringify(r.query));
    return {t:r.created,o:r.open,h:r.high,l:r.low,c:r.close};
  } catch(e) { console.log(e); }
}

(async function () {
  const fetchData = await fetchOHLC(yUrl);
  alert(fetchData);
})()