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Here you can see once again, I open my Visual Studio Code editor and my Chrome browser, and I already

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create an async function named test, which is empty.

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So first I'm going to print a statement outside the function.

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Console.log.

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Inside the parentheses one colon message.

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It's mean.

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This is our first message.

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Here we are going to understand how await function worked.

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And I'm going to copy this same message and paste it inside the async function.

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And I'm going to duplicate it two times.

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And also I'm going to change their ID to three and four.

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So first it's going to print our message one statement.

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Then it's going to call our function test which is a async function.

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Then it print our three statements inside the async function.

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And once again I'm going to print in our console another message message five.

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If I save this file you can see in my console it prints all the messages serially.

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Messi's one.

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Messi's two.

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Messi's three.

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Messi's four.

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Messi's five.

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From 2 to 4.

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They are all from async function.

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And now I'm going to type await method before the message.

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Three I already told you what is the meaning of await.

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Wait and complete the job until this work is done.

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Complete our another work.

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Then it's return to our await function and check.

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Is it finished or not?

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If finished then it print Messi's four.

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So I'm going to save this file once again.

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And you can see it's changed our sequence.

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You can see first it print Messi's one.

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Then I call our function test which is a async function.

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So it print his first statement two.

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Then it print await message main message three.

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But I also declare our function to wait as long as it is waiting, the message outside the test function

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will be printed.

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So after three it's print five, not four.

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As soon as the job is done, it came back again to check.

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Is it work properly or not?

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If it works properly then print Messi's four.

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So in that way our await method work in our async function.

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If we try to run await method without async function, then it's return error.

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And now I'm going to show you what is the actual use of await method, where and why we use await method.

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Whenever we try to face data from the server, then we need to use await method.

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So here I'm going to use fetch method and we learn about it in our previous video.

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And here I'm going to fetch a Json data.

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And I already created Json file in my current working directory.

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Let me show you here you can see I create a folder named contain.

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And inside this folder you can see a Json file named student dot Json.

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And we have three records in our file name age and city.

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It's a Json format.

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Also, you can retrieve fake Json data from website basically for testing purpose.

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So let's back to the index.html file.

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And now I'm going to use the fetch method.

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So first I'm going to create a variable.

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And I'm going to remove this line const response equal to fetch.

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And insert the fetch method.

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I'm going to pass my URL content slash student dot Json.

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So before this face function I'm going to use our method await its mean.

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I told my function to wait and fetch the complete data from our Json file until the process complete.

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It's run our next codes.

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As soon as all work is over.

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It's written to the await function and continue with next lines.

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We know our fetch method return a promise.

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So I'm going to create a variable.

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But first I'm going to remove this line.

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Const student equal to.

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And once again I'm going to use await method response dot Json.

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And we learn about it in our previous video.

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Basically our fetch method returned Json or text format.

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So in response we get Json file.

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So we need to use dot Json.

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And I'm going to return all the data which I retrieved from the Json file.

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Return student and return student value.

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And we know our async function return a promise.

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So first is going to print message one.

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And then it going to run my function test.

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It's a async function.

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So it's going to print message to.

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After that we are asking to wait here.

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After our first await function I'm going to print another message.

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Message three and also I'm going to create a variable for our function call.

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Let x equal to test.

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And I want to print this response in our console.

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So I'm going to type console dot log inside the round braces x.

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Let's save the code.

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You can see in my console.

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As you can see first it print matches one.

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And then we call our function test.

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So it's print masses too.

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And then I told it to wait.

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Here I am going to fetch data from server.

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So it's jump out of this function and started working on masses for.

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So you can see in my console section it prints four after two.

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And when masses four is complete we call our x variable.

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So it's going back to the async function.

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And it gets a response from server.

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And you can see it print our response as a promise.

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And you can see we have two array in our promise.

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And our promise state is fulfilled.

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After complete the promise section then it print our message.

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Three in that way we use async and await method with our fetch function.

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And now I'm going to remove all the extra messages.

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So I'm going to remove all the console section.

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Now it's looking pretty simple.

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First we run await function for our fetch content.

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It will keep waiting until the data comes from the server.

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And we told our response to wait once again.

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So I use another await method.

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Then we return our result.

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If I save this file, you can see in my console.

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As a result, we get a promise and we have two array in our promise because in our Json file we have

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two result.

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And as you know we can use then and catch function with promise method.

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So first I'm going to remove the console section.

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And also I'm going to remove this variable x.

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So first we call our test function.

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If it return promise successfully then we are going to use then function.

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And insert the then function, I'm going to create an arrow function.

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And also I'm going to create cash method.

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After that dot cash inside the parentheses I'm going to create another arrow function.

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If there is an error in our function then automatically it run catch function.

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And now I'm going to save student record in a variable.

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And our variable name is r e s.

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Data means response data.

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And I'm going to print this value in our console console dot log r e s data.

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And if there is an error in our code our catch method going to print another message error message.

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So I'm going to create another variable error inside the error function I'm going to print console dot

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log error.

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So first we called our async function test.

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And it return a promise.

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If promise is fulfilled then it run then function.

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And if there is an error in our function, it automatically run catch function.

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And if I save this file you can see in my console it returns an array.

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And if I open this array you can see it provides Json object.

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And if I change file path.

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So I'm going to remove S from student and save this file.

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You can see in my console it print an error for zero four means file not found.

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So it run our catch method and print the error.

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Now let's see how we can convert so many lines in a one line.

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I just want to make it one liner.

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So first I'm going to comment out all this line.

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Mainly we are focused on fetch and await method.

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So I'm going to return inside the parentheses I'm going to call await method.

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And I want to return Json format.

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So I use dot Json function.

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So we make it one liner.

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If I save this file you can see in my console.

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Similarly it returns an array and we have two Json object inside this array.

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So here you can see I convert three line of code into a one line.

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Let's talk about our last topic error handling.

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Basically we handle our error using catch function.

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There is a drawback using catch function.

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When we call test function every time we need to use catch method to handle the error.

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So I don't want to use every time.

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So there is a shortcut to handle it.

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So I'm going to uncomment all the lines and comment out this return section.

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Basically we use try or catch to handle this error.

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So inside the async function we use try or catch block.

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In our next video, we will learn more about try or catch inside the try block.

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We type our whole code.

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So I'm going to move this code inside the try block.

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It's mean.

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We are trying this code.

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If it worked properly then it return and we can access this in our then function.

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And if there is an error in this try block then it's automatically run catch block.

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And inside the catch block we print our error.

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So I'm going to move this error message in this block.

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And I'm going to remove the catch method.

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And also we need to declare the error variable inside the error block.

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So whenever we call test function then we don't need to type catch method to handle the error.

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And if I save this file you can see in my console we can access our data successfully.

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And if I create an error inside my function.

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So I'm going to change the response.

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Spelling is double to poncey.

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And you can see there is no variable name.

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Rest 22 pawns and we know it's going to return an error.

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In that case it will run our catch block.

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And if I save this file you can see an error in my console it print reference error rest 22 pawns is

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not defined at test, because we do not define this variable in our function and also it print another

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message undefined.

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So you can see how we can handle error using try or catch block.

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It is pretty similar with try except condition in Python.

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If there is an error in our try block, then it automatically jump to the catch block and it print our

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error message.

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And I'm going to resolve this problem and save this file once again.

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And now it's worked pretty fine.

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If you want to print this result in your document section you can you can use for loop for that.

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So I hope now it's clear for you what is async and await method and how we can use it with our fetch

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method.

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Thanks for watching this video.

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See you soon!