Check if certain props changed, no indexer

I am using TS 2.4 -

I have an object defined by interface:

interface Foo 
 name: string,
 version: number,
 qux: boolean,
 baz: boolean

I do not want an indexer in here. I now want to do a .some to see if certain props changed. These props are defined as strings in an array.

const significantProps = ['name', 'version'];

const foo: Foo = ;
const prevFoo: Foo = ;
const shouldUpdate = significantProps.some((prop: string) => foo[prop] !== prevFoo[prop]);

However this gives me error:

[ts] Element implicitly has an 'any' type because type 'Foo' has no index signature. [7017]

Is there a way to achieve this?

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

If you want to index things, you'll need an indexer. ...

– Ian MacDonald
Nov 14 '18 at 21:12

add a comment |

I am using TS 2.4 -

I have an object defined by interface:

interface Foo 
 name: string,
 version: number,
 qux: boolean,
 baz: boolean

I do not want an indexer in here. I now want to do a .some to see if certain props changed. These props are defined as strings in an array.

const significantProps = ['name', 'version'];

const foo: Foo = ;
const prevFoo: Foo = ;
const shouldUpdate = significantProps.some((prop: string) => foo[prop] !== prevFoo[prop]);

However this gives me error:

[ts] Element implicitly has an 'any' type because type 'Foo' has no index signature. [7017]

Is there a way to achieve this?

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

If you want to index things, you'll need an indexer. ...

– Ian MacDonald
Nov 14 '18 at 21:12

add a comment |

I am using TS 2.4 -

I have an object defined by interface:

interface Foo 
 name: string,
 version: number,
 qux: boolean,
 baz: boolean

I do not want an indexer in here. I now want to do a .some to see if certain props changed. These props are defined as strings in an array.

const significantProps = ['name', 'version'];

const foo: Foo = ;
const prevFoo: Foo = ;
const shouldUpdate = significantProps.some((prop: string) => foo[prop] !== prevFoo[prop]);

However this gives me error:

[ts] Element implicitly has an 'any' type because type 'Foo' has no index signature. [7017]

Is there a way to achieve this?

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

I am using TS 2.4 -

I have an object defined by interface:

interface Foo 
 name: string,
 version: number,
 qux: boolean,
 baz: boolean

I do not want an indexer in here. I now want to do a .some to see if certain props changed. These props are defined as strings in an array.

const significantProps = ['name', 'version'];

const foo: Foo = ;
const prevFoo: Foo = ;
const shouldUpdate = significantProps.some((prop: string) => foo[prop] !== prevFoo[prop]);

However this gives me error:

[ts] Element implicitly has an 'any' type because type 'Foo' has no index signature. [7017]

Is there a way to achieve this?

typescript

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

asked Nov 14 '18 at 21:06

Noitidart

18.3k1364162

If you want to index things, you'll need an indexer. ...

– Ian MacDonald
Nov 14 '18 at 21:12

add a comment |

If you want to index things, you'll need an indexer. ...

– Ian MacDonald
Nov 14 '18 at 21:12

If you want to index things, you'll need an indexer. ...

– Ian MacDonald
Nov 14 '18 at 21:12

add a comment |

1 Answer
1

active

oldest

votes

Redefine that array of keys to actually be an array of keyof Foo:

const significantProps: (keyof Foo) = ['name', 'version'];

const foo: Foo = as any;
const prevFoo: Foo = as any;
const shouldUpdate = significantProps.some((prop) => foo[prop] !== prevFoo[prop]);

answered Nov 14 '18 at 21:50

y2bd

1,198816

So cool!! I couldn't find keyof in the docs. May you please link me? I was looking for all the helper things like this in the docs, is there somewhere?

– Noitidart
Nov 14 '18 at 23:41

1

Sure, they’re over here: typescriptlang.org/docs/handbook/… (scroll down to Index Types).

– y2bd
Nov 15 '18 at 2:09

Thanks you @y2bd!

– Noitidart
Nov 15 '18 at 18:04

add a comment |

Your Answer

StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);

);

draft saved

draft discarded

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53308721%2fcheck-if-certain-props-changed-no-indexer%23new-answer', 'question_page');

);

Post as a guest

Name

Required, but never shown

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

Redefine that array of keys to actually be an array of keyof Foo:

const significantProps: (keyof Foo) = ['name', 'version'];

const foo: Foo = as any;
const prevFoo: Foo = as any;
const shouldUpdate = significantProps.some((prop) => foo[prop] !== prevFoo[prop]);

answered Nov 14 '18 at 21:50

y2bd

1,198816

So cool!! I couldn't find keyof in the docs. May you please link me? I was looking for all the helper things like this in the docs, is there somewhere?

– Noitidart
Nov 14 '18 at 23:41

1

Sure, they’re over here: typescriptlang.org/docs/handbook/… (scroll down to Index Types).

– y2bd
Nov 15 '18 at 2:09

Thanks you @y2bd!

– Noitidart
Nov 15 '18 at 18:04

add a comment |

Redefine that array of keys to actually be an array of keyof Foo:

const significantProps: (keyof Foo) = ['name', 'version'];

const foo: Foo = as any;
const prevFoo: Foo = as any;
const shouldUpdate = significantProps.some((prop) => foo[prop] !== prevFoo[prop]);

answered Nov 14 '18 at 21:50

y2bd

1,198816

So cool!! I couldn't find keyof in the docs. May you please link me? I was looking for all the helper things like this in the docs, is there somewhere?

– Noitidart
Nov 14 '18 at 23:41

1

Sure, they’re over here: typescriptlang.org/docs/handbook/… (scroll down to Index Types).

– y2bd
Nov 15 '18 at 2:09

Thanks you @y2bd!

– Noitidart
Nov 15 '18 at 18:04

add a comment |

Redefine that array of keys to actually be an array of keyof Foo:

const significantProps: (keyof Foo) = ['name', 'version'];

const foo: Foo = as any;
const prevFoo: Foo = as any;
const shouldUpdate = significantProps.some((prop) => foo[prop] !== prevFoo[prop]);

answered Nov 14 '18 at 21:50

y2bd

1,198816

Redefine that array of keys to actually be an array of keyof Foo:

const significantProps: (keyof Foo) = ['name', 'version'];

const foo: Foo = as any;
const prevFoo: Foo = as any;
const shouldUpdate = significantProps.some((prop) => foo[prop] !== prevFoo[prop]);

answered Nov 14 '18 at 21:50

y2bd

1,198816

answered Nov 14 '18 at 21:50

y2bd

1,198816

answered Nov 14 '18 at 21:50

y2bd

1,198816

answered Nov 14 '18 at 21:50

y2bd

1,198816

So cool!! I couldn't find keyof in the docs. May you please link me? I was looking for all the helper things like this in the docs, is there somewhere?

– Noitidart
Nov 14 '18 at 23:41

1

Sure, they’re over here: typescriptlang.org/docs/handbook/… (scroll down to Index Types).

– y2bd
Nov 15 '18 at 2:09

Thanks you @y2bd!

– Noitidart
Nov 15 '18 at 18:04

add a comment |

So cool!! I couldn't find keyof in the docs. May you please link me? I was looking for all the helper things like this in the docs, is there somewhere?

– Noitidart
Nov 14 '18 at 23:41

1

Sure, they’re over here: typescriptlang.org/docs/handbook/… (scroll down to Index Types).

– y2bd
Nov 15 '18 at 2:09

Thanks you @y2bd!

– Noitidart
Nov 15 '18 at 18:04

So cool!! I couldn't find keyof in the docs. May you please link me? I was looking for all the helper things like this in the docs, is there somewhere?

– Noitidart
Nov 14 '18 at 23:41

Sure, they’re over here: typescriptlang.org/docs/handbook/… (scroll down to Index Types).

– y2bd
Nov 15 '18 at 2:09

Thanks you @y2bd!

– Noitidart
Nov 15 '18 at 18:04

add a comment |

draft saved

draft discarded

Thanks for contributing an answer to Stack Overflow!

Please be sure to answer the question. Provide details and share your research!

But avoid …

Asking for help, clarification, or responding to other answers.

Making statements based on opinion; back them up with references or personal experience.

To learn more, see our tips on writing great answers.

draft saved

draft discarded

Post as a guest

Name

Required, but never shown

Name

Required, but never shown

Name

Required, but never shown

This page is only for reference, If you need detailed information, please check here

搜尋此網誌

Pfthb