Mixing
js: value is null, typeof returns string, but comparison with null or '' returns false
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ height:90px;width:728px;box-sizing:border-box;
}
Am evaluating koa js for a solution, but ran through the following issue:
Have some http headers which need not always be populated by the client, means sometimes the header will be null, but on processing the header on server side comparing it for null/empty string always returns false even when it is null.
To see whats the value and what the outcome of comparison is, have traced all the possible outcomes and here are the following:
console.log(typeof ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId'));
console.log(!ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId') === null);
console.log(ctx.get('X-SessionId') == null);
console.log(ctx.get('X-SessionId') == '');
console.log(ctx.get('X-SessionId') === '');
console.log(ctx.get('X-SessionId').length);
Output :
string
null
false
false
false
false
false
4
Here the typeof returns string but the value itself is null. Comparing it with either null or '' returns false. And surprisingly .length returns 4!
Anyone has a suggestion how to overcome this comparison problem?
node.js koa
asked Jan 3 at 5:56
Rayees KmRayees Km
32
add a comment |
Am evaluating koa js for a solution, but ran through the following issue:
Have some http headers which need not always be populated by the client, means sometimes the header will be null, but on processing the header on server side comparing it for null/empty string always returns false even when it is null.
To see whats the value and what the outcome of comparison is, have traced all the possible outcomes and here are the following:
console.log(typeof ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId'));
console.log(!ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId') === null);
console.log(ctx.get('X-SessionId') == null);
console.log(ctx.get('X-SessionId') == '');
console.log(ctx.get('X-SessionId') === '');
console.log(ctx.get('X-SessionId').length);
Output :
string
null
false
false
false
false
false
4
Here the typeof returns string but the value itself is null. Comparing it with either null or '' returns false. And surprisingly .length returns 4!
Anyone has a suggestion how to overcome this comparison problem?
node.js koa
asked Jan 3 at 5:56
Rayees KmRayees Km
32
1
literal "null" = 4 chars? Tryconsole.log(ctx.get('X-SessionId') === "null");
– Emma
Jan 3 at 6:01
Oh my God yes its literal 'null'. Cross checked whats being passed from client side. But there it says null and not "null". Normally any string thats passed on headers are contained in "", so am pretty sure the header is passed as null, Wondering why on the server side its taking as "null"? Anyways thanks a lot @Emma for this suggestion.
– Rayees Km
Jan 3 at 6:12
add a comment |
Am evaluating koa js for a solution, but ran through the following issue:
Have some http headers which need not always be populated by the client, means sometimes the header will be null, but on processing the header on server side comparing it for null/empty string always returns false even when it is null.
To see whats the value and what the outcome of comparison is, have traced all the possible outcomes and here are the following:
console.log(typeof ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId'));
console.log(!ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId') === null);
console.log(ctx.get('X-SessionId') == null);
console.log(ctx.get('X-SessionId') == '');
console.log(ctx.get('X-SessionId') === '');
console.log(ctx.get('X-SessionId').length);
Output :
string
null
false
false
false
false
false
4
Here the typeof returns string but the value itself is null. Comparing it with either null or '' returns false. And surprisingly .length returns 4!
Anyone has a suggestion how to overcome this comparison problem?
node.js koa
asked Jan 3 at 5:56
Rayees KmRayees Km
32
Am evaluating koa js for a solution, but ran through the following issue:
Have some http headers which need not always be populated by the client, means sometimes the header will be null, but on processing the header on server side comparing it for null/empty string always returns false even when it is null.
To see whats the value and what the outcome of comparison is, have traced all the possible outcomes and here are the following:
console.log(typeof ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId'));
console.log(!ctx.get('X-SessionId'));
console.log(ctx.get('X-SessionId') === null);
console.log(ctx.get('X-SessionId') == null);
console.log(ctx.get('X-SessionId') == '');
console.log(ctx.get('X-SessionId') === '');
console.log(ctx.get('X-SessionId').length);
Output :
string
null
false
false
false
false
false
4
Here the typeof returns string but the value itself is null. Comparing it with either null or '' returns false. And surprisingly .length returns 4!
Anyone has a suggestion how to overcome this comparison problem?
node.js koa
node.js koa
asked Jan 3 at 5:56
Rayees KmRayees Km
32
asked Jan 3 at 5:56
Rayees KmRayees Km
32
asked Jan 3 at 5:56
Rayees KmRayees Km
32
asked Jan 3 at 5:56
Rayees KmRayees Km
32
asked Jan 3 at 5:56
Rayees KmRayees Km
32
32
1
literal "null" = 4 chars? Tryconsole.log(ctx.get('X-SessionId') === "null");
– Emma
Jan 3 at 6:01
Oh my God yes its literal 'null'. Cross checked whats being passed from client side. But there it says null and not "null". Normally any string thats passed on headers are contained in "", so am pretty sure the header is passed as null, Wondering why on the server side its taking as "null"? Anyways thanks a lot @Emma for this suggestion.
– Rayees Km
Jan 3 at 6:12
add a comment |
1
literal "null" = 4 chars? Tryconsole.log(ctx.get('X-SessionId') === "null");
– Emma
Jan 3 at 6:01
Oh my God yes its literal 'null'. Cross checked whats being passed from client side. But there it says null and not "null". Normally any string thats passed on headers are contained in "", so am pretty sure the header is passed as null, Wondering why on the server side its taking as "null"? Anyways thanks a lot @Emma for this suggestion.
– Rayees Km
Jan 3 at 6:12
1
1
literal "null" = 4 chars? Try
console.log(ctx.get('X-SessionId') === "null");– Emma
Jan 3 at 6:01
literal "null" = 4 chars? Try
console.log(ctx.get('X-SessionId') === "null");– Emma
Jan 3 at 6:01
Oh my God yes its literal 'null'. Cross checked whats being passed from client side. But there it says null and not "null". Normally any string thats passed on headers are contained in "", so am pretty sure the header is passed as null, Wondering why on the server side its taking as "null"? Anyways thanks a lot @Emma for this suggestion.
– Rayees Km
Jan 3 at 6:12
Oh my God yes its literal 'null'. Cross checked whats being passed from client side. But there it says null and not "null". Normally any string thats passed on headers are contained in "", so am pretty sure the header is passed as null, Wondering why on the server side its taking as "null"? Anyways thanks a lot @Emma for this suggestion.
– Rayees Km
Jan 3 at 6:12
add a comment |
0
active
oldest
votes
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%2f54017027%2fjs-value-is-null-typeof-returns-string-but-comparison-with-null-or-returns%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
0
active
oldest
votes
0
active
oldest
votes
active
oldest
votes
active
oldest
votes
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%2f54017027%2fjs-value-is-null-typeof-returns-string-but-comparison-with-null-or-returns%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
1
literal "null" = 4 chars? Try
console.log(ctx.get('X-SessionId') === "null");– Emma
Jan 3 at 6:01
Oh my God yes its literal 'null'. Cross checked whats being passed from client side. But there it says null and not "null". Normally any string thats passed on headers are contained in "", so am pretty sure the header is passed as null, Wondering why on the server side its taking as "null"? Anyways thanks a lot @Emma for this suggestion.
– Rayees Km
Jan 3 at 6:12