Ways to evaluate a value in JavaScript

After performing an ajax operation to retrieve data, I am using javascript to perform conditional checks. Here is the output when printing the response:

document.write(response)

Result:

[object Object]

When printing something like

document.write(JSON.stringify(response))
, the result is:

Result:

{"status":"failed","login":["This field is required."],"password":["This field is required."]}

Based on the above data, I am attempting to implement the following logic:

if(response.status === 'failed')
            window.location.href = response.next;
        else if ('login' in response && response['login']==["This field is required."])
           {
              $("#message").html(<p>Username is required</p>); 
           }
        else if ('password' in response && response['password']==["This field is required."])
           {
              $("#message").html(<p>Password is required</p>); 
           }

However, the condition && with

response['login']==["This field is required."]
is not functioning as expected. How can I properly check the value in javascript?

Note: *New to javascript *

Answer №1

When working with the response object, make sure to utilize the dot operator to access its various properties.

response.login[0] === "This field is required."

For clarification, the response you receive is a JSON object. To access properties within a JSON object, simply use the .PropertyName syntax. In this case, the login property is an array, so to retrieve the first element, you use the [0] indexer. Remember to use the === operator when comparing strings in JavaScript for accurate type and value comparison.

Answer №2

Here's a better validation approach. It checks the first element of the login array.

response['login'][0] == "This field is required."

Answer №3

Due to the fact that arrays are not considered equal to other arrays, it is important to use response['login'][0] to compare the actual strings.

> var array1 = ['array'];

> array1 == ['array']
< false

> array1[0] == 'array'
< true

Answer №4

Eliminate the use of square brackets. This is an array. It needs to be compared as a string.

Answer №5

JSON serves as a portable form of Javascript syntax. Your comparison is not accurate. When a JSON string is decoded in Javascript, it transforms into a NATIVE JavaScript object/array. Therefore, when dealing with your example JSON string, the correct comparison should be

(response.password[0] == 'This field is required')

Take note of the absence of [] brackets around the "this field..." text. Your current code is essentially

if (string == array)

when it should be

if (string == string)

(maintaining the same positions for comparison elements).

Answer №6

Feel free to give this a shot:-

response['login'][0] == "This field is mandatory."

Answer №7

In JavaScript, you cannot use the == operator to compare arrays.

For example, {} == {} // false because two objects are not identical.

Similarly, new Foo() == new Foo(); // false

And also,

new Array() == new Array() // false

Just remember that [] is a shorthand for new Array() (even though it's a bit more complicated).

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