node js : why can't I write asynchronously in jason.js and then read it synchronously?

-1

Please can anyone help me with this?
my question is: why can't I write asynchronously in jason.js and then read it synchronously?

To make my question clear, here is my code:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

});



//here I read synchronously from the note.json file

var file = fs.readFileSync('./note.json');

var note = JSON.parse(file);

when I do this I get the following error:

SyntaxError: Unexpected end of JSON input



at JSON.parse (<anonymous>)



at Object.<anonymous> (/Users/yosra/Desktop/notes-node/playground/json.js:31:18)



at Module._compile (internal/modules/cjs/loader.js:721:30)



at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)



at Module.load (internal/modules/cjs/loader.js:620:32)



at tryModuleLoad (internal/modules/cjs/loader.js:560:12)



at Function.Module._load (internal/modules/cjs/loader.js:552:3)



at Function.Module.runMain (internal/modules/cjs/loader.js:774:12)



at executeUserCode (internal/bootstrap/node.js:342:17)



at startExecution (internal/bootstrap/node.js:276:5)

but when I make everything synchronous it works.

Thanks a lot

asked Jan 18 at 14:19

Yosra

New contributor

1

Are you sure you understand what "asynchronously" means? The .writeFile() function call returns immediately, before the file has actually been written.

– Pointy
Jan 18 at 14:22

@Pointy yes, synchronous code is executed in a linear way which is not the case for asynchonous code.

– Yosra
Jan 18 at 14:47

nodejs.org/dist/latest-v11.x/docs/api/… I may be wrong, but here they say that it doesn't return immediatly

– Yosra
Jan 18 at 14:49

"Asynchronously writes data to a file" — that means it returns immediately. The callback is invoked when the operation completes.

– Pointy
Jan 18 at 14:52

ooh yeah, of course thank you so much, I get it now :) .

– Yosra
Jan 18 at 15:04

add a comment |

-1

Please can anyone help me with this?
my question is: why can't I write asynchronously in jason.js and then read it synchronously?

To make my question clear, here is my code:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

});



//here I read synchronously from the note.json file

var file = fs.readFileSync('./note.json');

var note = JSON.parse(file);

when I do this I get the following error:

SyntaxError: Unexpected end of JSON input



at JSON.parse (<anonymous>)



at Object.<anonymous> (/Users/yosra/Desktop/notes-node/playground/json.js:31:18)



at Module._compile (internal/modules/cjs/loader.js:721:30)



at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)



at Module.load (internal/modules/cjs/loader.js:620:32)



at tryModuleLoad (internal/modules/cjs/loader.js:560:12)



at Function.Module._load (internal/modules/cjs/loader.js:552:3)



at Function.Module.runMain (internal/modules/cjs/loader.js:774:12)



at executeUserCode (internal/bootstrap/node.js:342:17)



at startExecution (internal/bootstrap/node.js:276:5)

but when I make everything synchronous it works.

Thanks a lot

asked Jan 18 at 14:19

Yosra

New contributor

1

Are you sure you understand what "asynchronously" means? The .writeFile() function call returns immediately, before the file has actually been written.

– Pointy
Jan 18 at 14:22

@Pointy yes, synchronous code is executed in a linear way which is not the case for asynchonous code.

– Yosra
Jan 18 at 14:47

nodejs.org/dist/latest-v11.x/docs/api/… I may be wrong, but here they say that it doesn't return immediatly

– Yosra
Jan 18 at 14:49

"Asynchronously writes data to a file" — that means it returns immediately. The callback is invoked when the operation completes.

– Pointy
Jan 18 at 14:52

ooh yeah, of course thank you so much, I get it now :) .

– Yosra
Jan 18 at 15:04

add a comment |

-1

Please can anyone help me with this?
my question is: why can't I write asynchronously in jason.js and then read it synchronously?

To make my question clear, here is my code:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

});



//here I read synchronously from the note.json file

var file = fs.readFileSync('./note.json');

var note = JSON.parse(file);

when I do this I get the following error:

SyntaxError: Unexpected end of JSON input



at JSON.parse (<anonymous>)



at Object.<anonymous> (/Users/yosra/Desktop/notes-node/playground/json.js:31:18)



at Module._compile (internal/modules/cjs/loader.js:721:30)



at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)



at Module.load (internal/modules/cjs/loader.js:620:32)



at tryModuleLoad (internal/modules/cjs/loader.js:560:12)



at Function.Module._load (internal/modules/cjs/loader.js:552:3)



at Function.Module.runMain (internal/modules/cjs/loader.js:774:12)



at executeUserCode (internal/bootstrap/node.js:342:17)



at startExecution (internal/bootstrap/node.js:276:5)

but when I make everything synchronous it works.

Thanks a lot

asked Jan 18 at 14:19

Yosra

New contributor

Please can anyone help me with this?
my question is: why can't I write asynchronously in jason.js and then read it synchronously?

To make my question clear, here is my code:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

});



//here I read synchronously from the note.json file

var file = fs.readFileSync('./note.json');

var note = JSON.parse(file);

when I do this I get the following error:

SyntaxError: Unexpected end of JSON input



at JSON.parse (<anonymous>)



at Object.<anonymous> (/Users/yosra/Desktop/notes-node/playground/json.js:31:18)



at Module._compile (internal/modules/cjs/loader.js:721:30)



at Object.Module._extensions..js (internal/modules/cjs/loader.js:732:10)



at Module.load (internal/modules/cjs/loader.js:620:32)



at tryModuleLoad (internal/modules/cjs/loader.js:560:12)



at Function.Module._load (internal/modules/cjs/loader.js:552:3)



at Function.Module.runMain (internal/modules/cjs/loader.js:774:12)



at executeUserCode (internal/bootstrap/node.js:342:17)



at startExecution (internal/bootstrap/node.js:276:5)

but when I make everything synchronous it works.

Thanks a lot

javascript node.js asynchronous synchronization

asked Jan 18 at 14:19

Yosra

New contributor

asked Jan 18 at 14:19

Yosra

New contributor

asked Jan 18 at 14:19

Yosra

New contributor

asked Jan 18 at 14:19

Yosra

asked Jan 18 at 14:19

Yosra

New contributor

Yosra is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

1

Are you sure you understand what "asynchronously" means? The .writeFile() function call returns immediately, before the file has actually been written.

– Pointy
Jan 18 at 14:22

@Pointy yes, synchronous code is executed in a linear way which is not the case for asynchonous code.

– Yosra
Jan 18 at 14:47

nodejs.org/dist/latest-v11.x/docs/api/… I may be wrong, but here they say that it doesn't return immediatly

– Yosra
Jan 18 at 14:49

"Asynchronously writes data to a file" — that means it returns immediately. The callback is invoked when the operation completes.

– Pointy
Jan 18 at 14:52

ooh yeah, of course thank you so much, I get it now :) .

– Yosra
Jan 18 at 15:04

add a comment |

1

Are you sure you understand what "asynchronously" means? The .writeFile() function call returns immediately, before the file has actually been written.

– Pointy
Jan 18 at 14:22

@Pointy yes, synchronous code is executed in a linear way which is not the case for asynchonous code.

– Yosra
Jan 18 at 14:47

nodejs.org/dist/latest-v11.x/docs/api/… I may be wrong, but here they say that it doesn't return immediatly

– Yosra
Jan 18 at 14:49

"Asynchronously writes data to a file" — that means it returns immediately. The callback is invoked when the operation completes.

– Pointy
Jan 18 at 14:52

ooh yeah, of course thank you so much, I get it now :) .

– Yosra
Jan 18 at 15:04

Are you sure you understand what "asynchronously" means? The .writeFile() function call returns immediately, before the file has actually been written.

– Pointy
Jan 18 at 14:22

@Pointy yes, synchronous code is executed in a linear way which is not the case for asynchonous code.

– Yosra
Jan 18 at 14:47

nodejs.org/dist/latest-v11.x/docs/api/… I may be wrong, but here they say that it doesn't return immediatly

– Yosra
Jan 18 at 14:49

"Asynchronously writes data to a file" — that means it returns immediately. The callback is invoked when the operation completes.

– Pointy
Jan 18 at 14:52

ooh yeah, of course thank you so much, I get it now :) .

– Yosra
Jan 18 at 15:04

add a comment |

2 Answers
2

active

oldest

votes

Welcome to Stack Overflow!

As for your questions, you are not handling async code correctly. your read should happen AFTER your write, so you should do the below:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

       //here I read synchronously from the note.json file

       var file = fs.readFileSync('./note.json');

       var note = JSON.parse(file);

});

answered Jan 18 at 14:27

LostJon

738211

Thank you so much

– Yosra
Jan 18 at 14:45

you are welcome. Can you please mark this as the answer so other folks may benefit? or select @Nicks answer from above. seems he and I answered at the same time (just about)

– LostJon
17 hours ago

add a comment |

You want to try to read the file after it's written. That means you have to do it in the callback function of writeFile.

//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

    console.log('hey there');

    //here I read synchronously from the note.json file

    var file = fs.readFileSync('./note.json');

    var note = JSON.parse(file);



});

answered Jan 18 at 14:26

Nick

3,1041420

Thank you so much I get it now

– Yosra
Jan 18 at 14:45

add a comment |

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2 Answers
2

active

oldest

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2 Answers
2

active

oldest

votes

Welcome to Stack Overflow!

As for your questions, you are not handling async code correctly. your read should happen AFTER your write, so you should do the below:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

       //here I read synchronously from the note.json file

       var file = fs.readFileSync('./note.json');

       var note = JSON.parse(file);

});

answered Jan 18 at 14:27

LostJon

738211

Thank you so much

– Yosra
Jan 18 at 14:45

you are welcome. Can you please mark this as the answer so other folks may benefit? or select @Nicks answer from above. seems he and I answered at the same time (just about)

– LostJon
17 hours ago

add a comment |

Welcome to Stack Overflow!

As for your questions, you are not handling async code correctly. your read should happen AFTER your write, so you should do the below:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

       //here I read synchronously from the note.json file

       var file = fs.readFileSync('./note.json');

       var note = JSON.parse(file);

});

answered Jan 18 at 14:27

LostJon

738211

Thank you so much

– Yosra
Jan 18 at 14:45

you are welcome. Can you please mark this as the answer so other folks may benefit? or select @Nicks answer from above. seems he and I answered at the same time (just about)

– LostJon
17 hours ago

add a comment |

Welcome to Stack Overflow!

As for your questions, you are not handling async code correctly. your read should happen AFTER your write, so you should do the below:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

       //here I read synchronously from the note.json file

       var file = fs.readFileSync('./note.json');

       var note = JSON.parse(file);

});

answered Jan 18 at 14:27

LostJon

738211

Welcome to Stack Overflow!

As for your questions, you are not handling async code correctly. your read should happen AFTER your write, so you should do the below:

const fs = require('fs');



var originalNote = {

   title: 'todo list',

   body : `that's my secret`

};



var stringNote = JSON.stringify(originalNote);



//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

       console.log('hey there');

       //here I read synchronously from the note.json file

       var file = fs.readFileSync('./note.json');

       var note = JSON.parse(file);

});

answered Jan 18 at 14:27

LostJon

738211

answered Jan 18 at 14:27

LostJon

738211

answered Jan 18 at 14:27

LostJon

738211

answered Jan 18 at 14:27

LostJon

738211

Thank you so much

– Yosra
Jan 18 at 14:45

you are welcome. Can you please mark this as the answer so other folks may benefit? or select @Nicks answer from above. seems he and I answered at the same time (just about)

– LostJon
17 hours ago

add a comment |

Thank you so much

– Yosra
Jan 18 at 14:45

you are welcome. Can you please mark this as the answer so other folks may benefit? or select @Nicks answer from above. seems he and I answered at the same time (just about)

– LostJon
17 hours ago

Thank you so much

– Yosra
Jan 18 at 14:45

you are welcome. Can you please mark this as the answer so other folks may benefit? or select @Nicks answer from above. seems he and I answered at the same time (just about)

– LostJon
17 hours ago

add a comment |

You want to try to read the file after it's written. That means you have to do it in the callback function of writeFile.

//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

    console.log('hey there');

    //here I read synchronously from the note.json file

    var file = fs.readFileSync('./note.json');

    var note = JSON.parse(file);



});

answered Jan 18 at 14:26

Nick

3,1041420

Thank you so much I get it now

– Yosra
Jan 18 at 14:45

add a comment |

You want to try to read the file after it's written. That means you have to do it in the callback function of writeFile.

//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

    console.log('hey there');

    //here I read synchronously from the note.json file

    var file = fs.readFileSync('./note.json');

    var note = JSON.parse(file);



});

answered Jan 18 at 14:26

Nick

3,1041420

Thank you so much I get it now

– Yosra
Jan 18 at 14:45

add a comment |

You want to try to read the file after it's written. That means you have to do it in the callback function of writeFile.

//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

    console.log('hey there');

    //here I read synchronously from the note.json file

    var file = fs.readFileSync('./note.json');

    var note = JSON.parse(file);



});

answered Jan 18 at 14:26

Nick

3,1041420

You want to try to read the file after it's written. That means you have to do it in the callback function of writeFile.

//here I write asynchronously into my note.json file

fs.writeFile('note.json',stringNote, () => {

    console.log('hey there');

    //here I read synchronously from the note.json file

    var file = fs.readFileSync('./note.json');

    var note = JSON.parse(file);



});

answered Jan 18 at 14:26

Nick

3,1041420

answered Jan 18 at 14:26

Nick

3,1041420

answered Jan 18 at 14:26

Nick

3,1041420

answered Jan 18 at 14:26

Nick

3,1041420

Thank you so much I get it now

– Yosra
Jan 18 at 14:45

add a comment |

Thank you so much I get it now

– Yosra
Jan 18 at 14:45

Thank you so much I get it now

– Yosra
Jan 18 at 14:45

add a comment |

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