Check something exists in array before executing

I have a array below that is constantly changing. It is being using in a node.js app. I have everything working good that updates elements of the array but if I restart node and the browser is still running, the webpage still sends data and causes it to crash, so I need to check if array exists before it tries to do something.

My array is like this, called users :-

[ { username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' } ]

So I need to check username 'a' exists. I have tried

users.map(obj => obj.username).indexOf(value) >= 0;

but doesnt work?

Any suggestions?

Thanks

asked Nov 24 '18 at 21:45

larry chambers

949

3

users.some( obj => obj.username === 'a' )?

– David Thomas
Nov 24 '18 at 21:48

It was on here somewhere, supposed to give a true or false if exists

– larry chambers
Nov 24 '18 at 21:49

1

return users.find(user => user.username === 'a'); or as Thomas wrote. return users.some(user => user.username);

– Adam Orlov
Nov 24 '18 at 21:52

1

Seems to work fine

– trincot
Nov 24 '18 at 21:56

Wierd, that works great in jsfiddle but I get this error when added to my script result = users.map(obj => obj.username).indexOf(value) >= 0; ^ ReferenceError: value is not defined

– larry chambers
Nov 24 '18 at 22:10

|
show 1 more comment

My array is like this, called users :-

[ { username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' } ]

So I need to check username 'a' exists. I have tried

users.map(obj => obj.username).indexOf(value) >= 0;

but doesnt work?

Any suggestions?

Thanks

asked Nov 24 '18 at 21:45

larry chambers

949

3

users.some( obj => obj.username === 'a' )?

– David Thomas
Nov 24 '18 at 21:48

It was on here somewhere, supposed to give a true or false if exists

– larry chambers
Nov 24 '18 at 21:49

1

return users.find(user => user.username === 'a'); or as Thomas wrote. return users.some(user => user.username);

– Adam Orlov
Nov 24 '18 at 21:52

1

Seems to work fine

– trincot
Nov 24 '18 at 21:56

Wierd, that works great in jsfiddle but I get this error when added to my script result = users.map(obj => obj.username).indexOf(value) >= 0; ^ ReferenceError: value is not defined

– larry chambers
Nov 24 '18 at 22:10

|
show 1 more comment

My array is like this, called users :-

[ { username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' } ]

So I need to check username 'a' exists. I have tried

users.map(obj => obj.username).indexOf(value) >= 0;

but doesnt work?

Any suggestions?

Thanks

asked Nov 24 '18 at 21:45

larry chambers

949

My array is like this, called users :-

[ { username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' } ]

So I need to check username 'a' exists. I have tried

users.map(obj => obj.username).indexOf(value) >= 0;

but doesnt work?

Any suggestions?

Thanks

javascript jquery

asked Nov 24 '18 at 21:45

larry chambers

949

asked Nov 24 '18 at 21:45

larry chambers

949

asked Nov 24 '18 at 21:45

larry chambers

949

asked Nov 24 '18 at 21:45

larry chambers

949

asked Nov 24 '18 at 21:45

larry chambers

949

3

users.some( obj => obj.username === 'a' )?

– David Thomas
Nov 24 '18 at 21:48

It was on here somewhere, supposed to give a true or false if exists

– larry chambers
Nov 24 '18 at 21:49

1

return users.find(user => user.username === 'a'); or as Thomas wrote. return users.some(user => user.username);

– Adam Orlov
Nov 24 '18 at 21:52

1

Seems to work fine

– trincot
Nov 24 '18 at 21:56

Wierd, that works great in jsfiddle but I get this error when added to my script result = users.map(obj => obj.username).indexOf(value) >= 0; ^ ReferenceError: value is not defined

– larry chambers
Nov 24 '18 at 22:10

|
show 1 more comment

3

users.some( obj => obj.username === 'a' )?

– David Thomas
Nov 24 '18 at 21:48

It was on here somewhere, supposed to give a true or false if exists

– larry chambers
Nov 24 '18 at 21:49

1

return users.find(user => user.username === 'a'); or as Thomas wrote. return users.some(user => user.username);

– Adam Orlov
Nov 24 '18 at 21:52

1

Seems to work fine

– trincot
Nov 24 '18 at 21:56

Wierd, that works great in jsfiddle but I get this error when added to my script result = users.map(obj => obj.username).indexOf(value) >= 0; ^ ReferenceError: value is not defined

– larry chambers
Nov 24 '18 at 22:10

users.some( obj => obj.username === 'a' )?

– David Thomas
Nov 24 '18 at 21:48

It was on here somewhere, supposed to give a true or false if exists

– larry chambers
Nov 24 '18 at 21:49

return users.find(user => user.username === 'a'); or as Thomas wrote. return users.some(user => user.username);

– Adam Orlov
Nov 24 '18 at 21:52

Seems to work fine

– trincot
Nov 24 '18 at 21:56

Wierd, that works great in jsfiddle but I get this error when added to my script result = users.map(obj => obj.username).indexOf(value) >= 0; ^ ReferenceError: value is not defined

– larry chambers
Nov 24 '18 at 22:10

|
show 1 more comment

1 Answer
1

active

oldest

votes

If you're looking to remve the users that don't have a username, then you could do something like this.

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

Otherwise, you should just use something like every

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

Or findIndex

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

If you're looking to remve the users that don't have a username, then you could do something like this.

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

Otherwise, you should just use something like every

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

Or findIndex

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

add a comment |

If you're looking to remve the users that don't have a username, then you could do something like this.

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

Otherwise, you should just use something like every

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

Or findIndex

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

add a comment |

If you're looking to remve the users that don't have a username, then you could do something like this.

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

Otherwise, you should just use something like every

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

Or findIndex

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

If you're looking to remve the users that don't have a username, then you could do something like this.

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

Otherwise, you should just use something like every

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

Or findIndex

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

const data = [{ 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

   { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];

    

    

console.log(data.filter(({username})=> username && username !== null));

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

const data = [ { 

    username: undefined,

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' },

    { 

    username: 'a',

    active: true,

    lat: '52.4099584',

    lng: '-1.5310848' }];





console.log(data.every(({username})=> username && username !== null));

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

const data = [ { 

        username: undefined,

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' },

        { 

        username: 'a',

        active: true,

        lat: '52.4099584',

        lng: '-1.5310848' }];





    console.log(data.findIndex(({username})=> !username || username === null) > -1);

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

answered Nov 24 '18 at 21:53

kemicofa

10.6k43983

add a comment |

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