Why is my string comparison in fetch response not working properly?

Question

Basically, I am posting id of draft to server to delete draft using fetch and server will response with success text if it succeeds. Here is my code.

fetch(this.url + "/vue/api/processdraft?action=delete&id=" + item.id, {
    method: "POST"
})
    .then(response => {
        return response.text();
    })
    .then(function (response) {
        console.log(response);
        if (response === "success") {
            console.log("Test");
            this.draftList.splice(index, 1);
        }
    });

In above code, in console.log(response) shows success as expected. But code inside if block doesn't work. And I cannot figure out what is wrong with it? It won't even print Test as it is supposed to. Here is screenshot of output.

And I've also checked that there is no white space before or after response text if it matters.

Edit: I checked for whitespaces in serverside and although I made sure there were no whitespace, but forgot to consider newline character. So this've been solved using trim() as suggested by answers.

`response.trim()` also see https://stackoverflow.com/questions/10805125/how-to-remove-all-line-breaks-from-a-string — kemicofa ghost, Sep 16 '19 at 08:29
`I've also checked that there is no white space before or after response text if it matters` - how? what is `console.log(response.length)` — Jaromanda X, Sep 16 '19 at 08:32
Possible duplicate of [How to remove all line breaks from a string](https://stackoverflow.com/questions/10805125/how-to-remove-all-line-breaks-from-a-string) — kemicofa ghost, Sep 16 '19 at 08:37
Depending on your needs you could also test for a success status code instead of the text response. `response.status < 400` or of you want to specifically test for a 2xx status simply `response.ok`. See the [Response properties](https://developer.mozilla.org/en-US/docs/Web/API/Response#Properties). However if you need to specifically match body text this might not fit your scenario. — 3limin4t0r, Sep 16 '19 at 08:41
fyi, newline characters are also considered whitespace characters. When you say *"I checked for whitespaces"* you meant "I checked for spaces". — 3limin4t0r, Sep 16 '19 at 08:47

Jonas Wilms · Answer 1 · 2019-09-16T08:31:00.273

1

There might be characters you don't see in the console (newlines, spaces, ...). To show them, you can use JSON.stringify:

    console.log(" success\n"); // success, right?
    console.log(JSON.stringify(" success\n")); // no, not quite ...

To match while ignoring whitespace and newlines, use response.trim() === "success", or response.includes("success").

edited Sep 16 '19 at 08:31

answered Sep 16 '19 at 08:29

Jonas Wilms

132,000
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This question might not even have needed an answer imo. – kemicofa ghost Sep 16 '19 at 08:30
Leaving a comment to answer this basic question is good enough, also closing it as a dup would also be good. There are plenty of answers talkinga bout how to remove spaces and new lines from strings. But just my opinion. Doesnt' matter in any case. – kemicofa ghost Sep 16 '19 at 08:33
but OP determined no whitespace – Jaromanda X Sep 16 '19 at 08:33
the OP states he has checked for whitespace – Jaromanda X Sep 16 '19 at 08:34
@kemicofa if you have a good dupe at hand, I'll be glad to close-vote – Jonas Wilms Sep 16 '19 at 08:35

score 1 · Accepted Answer · answered Sep 16 '19 at 08:32

1

You can try to use tim():

.then(function (response) {
    console.log(response);
    if (response.trim() === "success") {
        console.log("Test");
        this.draftList.splice(index, 1);
    }
});

Hope it'll work.

answered Sep 16 '19 at 08:32

P4uB0rd4

175
5

that would remove "whitespace", yeah? but the OP has checked and there are none – Jaromanda X Sep 16 '19 at 08:32
@JaromandaX maybe if we check the typeof the Response we can see if the === comparation works properly. – P4uB0rd4 Sep 16 '19 at 08:40

Why is my string comparison in fetch response not working properly?

2 Answers2