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Javascript promises not acting synchronously

Posted by: admin June 30, 2018 Leave a comment


I am attempting to use JavaScript promises so that the rest of my code waits for my asynchronous ‘chrome.storage.local.get’ call. However, it seems that the code is still acting asynchronously, and as a result sending undefined data out.

JavaScript code:

chrome.runtime.onMessage.addListener(function(request, sender, sendResponse) {

    if( request.message === "fetch-local-storage" ){//if popup request local data

        var responseData;

        let store = new Promise(function(resolve, reject){
            chrome.storage.local.get('localSearchList', function(query){
                responseData = query.localSearchList;
                resolve(responseData); // <- pass responseData to then()
            }); //fetch the local storage data 

        store.then(function(responseData){ // <= response data will be avaialble in then, executing ONLY after the asych get call is executed
            sendResponse({message: "local-storage-data", data: JSON.stringify(responseData)});


The console shows the following output:

The data being sent to popup (via content.js pipeline): undefined
asynch data: "[{\"word\":\"mo\",\"color\":\"rgb(128,0,128)\",\"id\":\"0\"}]"

If you look back at the code, this display shows that it is not working synchronously…