Mixing
Chaining JS Set methods results in TypeError
Why does
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by), new Set());
work as expected (the set gets two things added each iteration), whereas adding .delete("admin") as in
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by).delete("admin"), new Set());
results in TypeError: acc.add is not a function
javascript set
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
add a comment |
Why does
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by), new Set());
work as expected (the set gets two things added each iteration), whereas adding .delete("admin") as in
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by).delete("admin"), new Set());
results in TypeError: acc.add is not a function
javascript set
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
add a comment |
Why does
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by), new Set());
work as expected (the set gets two things added each iteration), whereas adding .delete("admin") as in
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by).delete("admin"), new Set());
results in TypeError: acc.add is not a function
javascript set
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
Why does
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by), new Set());
work as expected (the set gets two things added each iteration), whereas adding .delete("admin") as in
screens.reduce((acc,s) =>
acc.add(s._created_by).add(s._last_modified_by).delete("admin"), new Set());
results in TypeError: acc.add is not a function
javascript set
javascript set
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
asked Nov 22 '18 at 8:16
Simon HSimon H
12.8k74477
12.8k74477
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Check the docs for Set.prototype.delete:
Return value
trueif an element in the Set object has been removed successfully; otherwisefalse
It doesn't return the Set. So, if you want to use reduce and delete like that, you'll have to use two different statements, not just one chained one:
screens.reduce((acc,s) => {
acc
.add(s._created_by)
.add(s._last_modified_by)
.delete("admin");
return acc;
} , new Set());
(I suppose you could also use the comma operator to avoid having to use {/} blocks, but only for the sake of golfing, it would hurt code clarity)
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
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
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53426507%2fchaining-js-set-methods-results-in-typeerror%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Check the docs for Set.prototype.delete:
Return value
trueif an element in the Set object has been removed successfully; otherwisefalse
It doesn't return the Set. So, if you want to use reduce and delete like that, you'll have to use two different statements, not just one chained one:
screens.reduce((acc,s) => {
acc
.add(s._created_by)
.add(s._last_modified_by)
.delete("admin");
return acc;
} , new Set());
(I suppose you could also use the comma operator to avoid having to use {/} blocks, but only for the sake of golfing, it would hurt code clarity)
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
add a comment |
Check the docs for Set.prototype.delete:
Return value
trueif an element in the Set object has been removed successfully; otherwisefalse
It doesn't return the Set. So, if you want to use reduce and delete like that, you'll have to use two different statements, not just one chained one:
screens.reduce((acc,s) => {
acc
.add(s._created_by)
.add(s._last_modified_by)
.delete("admin");
return acc;
} , new Set());
(I suppose you could also use the comma operator to avoid having to use {/} blocks, but only for the sake of golfing, it would hurt code clarity)
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
add a comment |
Check the docs for Set.prototype.delete:
Return value
trueif an element in the Set object has been removed successfully; otherwisefalse
It doesn't return the Set. So, if you want to use reduce and delete like that, you'll have to use two different statements, not just one chained one:
screens.reduce((acc,s) => {
acc
.add(s._created_by)
.add(s._last_modified_by)
.delete("admin");
return acc;
} , new Set());
(I suppose you could also use the comma operator to avoid having to use {/} blocks, but only for the sake of golfing, it would hurt code clarity)
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
Check the docs for Set.prototype.delete:
Return value
trueif an element in the Set object has been removed successfully; otherwisefalse
It doesn't return the Set. So, if you want to use reduce and delete like that, you'll have to use two different statements, not just one chained one:
screens.reduce((acc,s) => {
acc
.add(s._created_by)
.add(s._last_modified_by)
.delete("admin");
return acc;
} , new Set());
(I suppose you could also use the comma operator to avoid having to use {/} blocks, but only for the sake of golfing, it would hurt code clarity)
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
edited Nov 22 '18 at 8:32
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
answered Nov 22 '18 at 8:19
CertainPerformanceCertainPerformance
89.4k164977
89.4k164977
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
add a comment |
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
OMG - JS still has some way to go to behave like a functional language - thanks!!!!
– Simon H
Nov 22 '18 at 8:21
add a comment |
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.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53426507%2fchaining-js-set-methods-results-in-typeerror%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
