Asynchronous function within for loop in javascript











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I have a two dimensional array name:final_draft_arr and I am looping through each element of this array and calling a function name:getFileContentAsBase64 with each element of the array. The function is asynchronous and the for is finish before the function is executed properly for each element. How to solve this asynchronous behavior. I want the function to execute before the loop goes to its next iteration. The codes are given below.



    getFileContentAsBase64:async function(path,callback){
await window.resolveLocalFileSystemURL(path, gotFile);
function gotFile(fileEntry) {
fileEntry.file(function(file) {
var reader = new FileReader();
reader.onloadend = function(e) {
var content = this.result;
callback(content);
};
reader.readAsDataURL(file);
});
}
},

base64ToBlob:function(base64, mime) {
mime = mime || '';
var sliceSize = 1024;
var byteChars = window.atob(base64);
var byteArrays = ;

for (var offset = 0, len = byteChars.length; offset < len; offset += sliceSize) {
var slice = byteChars.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
return new Blob(byteArrays, {type: mime});
},

//this is the loop
var final_draft_arr = JSON.parse(retrievedData);
$.each(final_draft_arr, function(key, value){
var i_dat = new FormData();
var data_id_no = final_draft_arr[key][0];
var sub_arr_len = final_draft_arr[key].length;
for(j=1; j < sub_arr_len; j++){
getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
var blob_new = base64ToBlob(base64ImageContent, 'image/png');
i_dat.append('Bilder', blob_new);

});
}

});









share|improve this question






















  • you need an await on the getFileContentAsbase64 function and the loop to be inside an async function. Also swap your $.each to a for loop. Not sure if you can do an await inside a $.each
    – JustLearning
    Nov 22 at 10:50















up vote
-1
down vote

favorite












I have a two dimensional array name:final_draft_arr and I am looping through each element of this array and calling a function name:getFileContentAsBase64 with each element of the array. The function is asynchronous and the for is finish before the function is executed properly for each element. How to solve this asynchronous behavior. I want the function to execute before the loop goes to its next iteration. The codes are given below.



    getFileContentAsBase64:async function(path,callback){
await window.resolveLocalFileSystemURL(path, gotFile);
function gotFile(fileEntry) {
fileEntry.file(function(file) {
var reader = new FileReader();
reader.onloadend = function(e) {
var content = this.result;
callback(content);
};
reader.readAsDataURL(file);
});
}
},

base64ToBlob:function(base64, mime) {
mime = mime || '';
var sliceSize = 1024;
var byteChars = window.atob(base64);
var byteArrays = ;

for (var offset = 0, len = byteChars.length; offset < len; offset += sliceSize) {
var slice = byteChars.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
return new Blob(byteArrays, {type: mime});
},

//this is the loop
var final_draft_arr = JSON.parse(retrievedData);
$.each(final_draft_arr, function(key, value){
var i_dat = new FormData();
var data_id_no = final_draft_arr[key][0];
var sub_arr_len = final_draft_arr[key].length;
for(j=1; j < sub_arr_len; j++){
getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
var blob_new = base64ToBlob(base64ImageContent, 'image/png');
i_dat.append('Bilder', blob_new);

});
}

});









share|improve this question






















  • you need an await on the getFileContentAsbase64 function and the loop to be inside an async function. Also swap your $.each to a for loop. Not sure if you can do an await inside a $.each
    – JustLearning
    Nov 22 at 10:50













up vote
-1
down vote

favorite









up vote
-1
down vote

favorite











I have a two dimensional array name:final_draft_arr and I am looping through each element of this array and calling a function name:getFileContentAsBase64 with each element of the array. The function is asynchronous and the for is finish before the function is executed properly for each element. How to solve this asynchronous behavior. I want the function to execute before the loop goes to its next iteration. The codes are given below.



    getFileContentAsBase64:async function(path,callback){
await window.resolveLocalFileSystemURL(path, gotFile);
function gotFile(fileEntry) {
fileEntry.file(function(file) {
var reader = new FileReader();
reader.onloadend = function(e) {
var content = this.result;
callback(content);
};
reader.readAsDataURL(file);
});
}
},

base64ToBlob:function(base64, mime) {
mime = mime || '';
var sliceSize = 1024;
var byteChars = window.atob(base64);
var byteArrays = ;

for (var offset = 0, len = byteChars.length; offset < len; offset += sliceSize) {
var slice = byteChars.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
return new Blob(byteArrays, {type: mime});
},

//this is the loop
var final_draft_arr = JSON.parse(retrievedData);
$.each(final_draft_arr, function(key, value){
var i_dat = new FormData();
var data_id_no = final_draft_arr[key][0];
var sub_arr_len = final_draft_arr[key].length;
for(j=1; j < sub_arr_len; j++){
getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
var blob_new = base64ToBlob(base64ImageContent, 'image/png');
i_dat.append('Bilder', blob_new);

});
}

});









share|improve this question













I have a two dimensional array name:final_draft_arr and I am looping through each element of this array and calling a function name:getFileContentAsBase64 with each element of the array. The function is asynchronous and the for is finish before the function is executed properly for each element. How to solve this asynchronous behavior. I want the function to execute before the loop goes to its next iteration. The codes are given below.



    getFileContentAsBase64:async function(path,callback){
await window.resolveLocalFileSystemURL(path, gotFile);
function gotFile(fileEntry) {
fileEntry.file(function(file) {
var reader = new FileReader();
reader.onloadend = function(e) {
var content = this.result;
callback(content);
};
reader.readAsDataURL(file);
});
}
},

base64ToBlob:function(base64, mime) {
mime = mime || '';
var sliceSize = 1024;
var byteChars = window.atob(base64);
var byteArrays = ;

for (var offset = 0, len = byteChars.length; offset < len; offset += sliceSize) {
var slice = byteChars.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
var byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
return new Blob(byteArrays, {type: mime});
},

//this is the loop
var final_draft_arr = JSON.parse(retrievedData);
$.each(final_draft_arr, function(key, value){
var i_dat = new FormData();
var data_id_no = final_draft_arr[key][0];
var sub_arr_len = final_draft_arr[key].length;
for(j=1; j < sub_arr_len; j++){
getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
var blob_new = base64ToBlob(base64ImageContent, 'image/png');
i_dat.append('Bilder', blob_new);

});
}

});






javascript






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asked Nov 22 at 10:47









Mohammad Syeduzzaman

83




83












  • you need an await on the getFileContentAsbase64 function and the loop to be inside an async function. Also swap your $.each to a for loop. Not sure if you can do an await inside a $.each
    – JustLearning
    Nov 22 at 10:50


















  • you need an await on the getFileContentAsbase64 function and the loop to be inside an async function. Also swap your $.each to a for loop. Not sure if you can do an await inside a $.each
    – JustLearning
    Nov 22 at 10:50
















you need an await on the getFileContentAsbase64 function and the loop to be inside an async function. Also swap your $.each to a for loop. Not sure if you can do an await inside a $.each
– JustLearning
Nov 22 at 10:50




you need an await on the getFileContentAsbase64 function and the loop to be inside an async function. Also swap your $.each to a for loop. Not sure if you can do an await inside a $.each
– JustLearning
Nov 22 at 10:50












1 Answer
1






active

oldest

votes

















up vote
1
down vote



accepted










Use async function as a callback and await the asynchronous function call.



$.each(final_draft_arr, async function(key, value){
var i_dat = new FormData();
var data_id_no = final_draft_arr[key][0];
var sub_arr_len = final_draft_arr[key].length;
for(j=1; j < sub_arr_len; j++){
await getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
var blob_new = base64ToBlob(base64ImageContent, 'image/png');
i_dat.append('Bilder', blob_new);

});
}
});





share|improve this answer





















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    1 Answer
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    active

    oldest

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    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    1
    down vote



    accepted










    Use async function as a callback and await the asynchronous function call.



    $.each(final_draft_arr, async function(key, value){
    var i_dat = new FormData();
    var data_id_no = final_draft_arr[key][0];
    var sub_arr_len = final_draft_arr[key].length;
    for(j=1; j < sub_arr_len; j++){
    await getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
    var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
    var blob_new = base64ToBlob(base64ImageContent, 'image/png');
    i_dat.append('Bilder', blob_new);

    });
    }
    });





    share|improve this answer

























      up vote
      1
      down vote



      accepted










      Use async function as a callback and await the asynchronous function call.



      $.each(final_draft_arr, async function(key, value){
      var i_dat = new FormData();
      var data_id_no = final_draft_arr[key][0];
      var sub_arr_len = final_draft_arr[key].length;
      for(j=1; j < sub_arr_len; j++){
      await getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
      var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
      var blob_new = base64ToBlob(base64ImageContent, 'image/png');
      i_dat.append('Bilder', blob_new);

      });
      }
      });





      share|improve this answer























        up vote
        1
        down vote



        accepted







        up vote
        1
        down vote



        accepted






        Use async function as a callback and await the asynchronous function call.



        $.each(final_draft_arr, async function(key, value){
        var i_dat = new FormData();
        var data_id_no = final_draft_arr[key][0];
        var sub_arr_len = final_draft_arr[key].length;
        for(j=1; j < sub_arr_len; j++){
        await getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
        var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
        var blob_new = base64ToBlob(base64ImageContent, 'image/png');
        i_dat.append('Bilder', blob_new);

        });
        }
        });





        share|improve this answer












        Use async function as a callback and await the asynchronous function call.



        $.each(final_draft_arr, async function(key, value){
        var i_dat = new FormData();
        var data_id_no = final_draft_arr[key][0];
        var sub_arr_len = final_draft_arr[key].length;
        for(j=1; j < sub_arr_len; j++){
        await getFileContentAsBase64(final_draft_arr[key][j],function(base64Image){
        var base64ImageContent = base64Image.replace(/^data:image/jpeg;base64,/, "");
        var blob_new = base64ToBlob(base64ImageContent, 'image/png');
        i_dat.append('Bilder', blob_new);

        });
        }
        });






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 22 at 10:50









        Easwar

        7448




        7448






























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