Make sure that when accessing an object, any undefined values do not cause the entire application to break

Question

Make sure that when accessing an object, any undefined values do not cause the entire application to break

One frustrating aspect of developing a JavaScript app is dealing with nested objects that can potentially cause errors and crash the entire application.

if(result.applicant._id === null || applicant_id !== result.applicant._id.toString()){
console.log('redirect user');
}

Looking at the code above, it's evident that there is a risk involved. What if result.applicant._id is null? In that case, calling toString() on an undefined value will result in an error. How can we ensure that toString() works properly in this scenario?

if(result.applicant._id === null || applicant_id !== (result.applicant._id && result.applicant._id.toString())){}

However, this solution feels messy and involves unnecessary duplication just to check for the existence of a property in JavaScript.

javascript

Answer 1

Answer №1

This version of the code functions effectively without ever encountering undefined.toString() because the if condition will be short-circuited when result.applicant._id === null evaluates to true, preventing the evaluation of

applicant_id !== result.applicant._id.toString()

.

The necessary test is already in place, so there is no need for additional checks in this scenario.

Update: Upon realization that === will not match undefined, simply modify the first part to result.applicant._id == null to properly match both undefined and null.

if (result.applicant._id == null || applicant_id !== result.applicant._id.toString()){
    console.log('redirect user');
}

You may encounter some linting warnings, but in this case, it is precisely what you want.

Answer 2

This version of the code functions effectively without ever encountering undefined.toString() because the if condition will be short-circuited when result.applicant._id === null evaluates to true, preventing the evaluation of

applicant_id !== result.applicant._id.toString()

.

The necessary test is already in place, so there is no need for additional checks in this scenario.

Update: Upon realization that === will not match undefined, simply modify the first part to result.applicant._id == null to properly match both undefined and null.

if (result.applicant._id == null || applicant_id !== result.applicant._id.toString()){
    console.log('redirect user');
}

You may encounter some linting warnings, but in this case, it is precisely what you want.

Answer 3

Answer №2

If you're looking to improve the clarity of your code, you might consider using some shorthand techniques. Just make sure that 0 isn't a valid application ID:

const id = result.application._id || 0;
if(!id || applicant_id !== id.toString()){
  // redirect
}

Update: Let me clarify - the || operator in the variable assignment will choose the first truthy value it encounters, or the second one if the first is undefined. So, even if the value defaults to 0, which is falsey, the check will still fail unless you convert it to a string.

Update 2: If your IDs are purely numerical (as they appear to be), there's no need to convert them to strings. Let JavaScript handle coercion for you by using != instead of !==.

const id = result.application._id || 0;
if(!id || applicant_id != id){
 // redirect
}

In JavaScript, 12 == '12' evaluates to true while 12 === '12' evaluates to false. It's generally recommended to use === unless you explicitly want to rely on type coercion, and this situation seems like a good fit for it :)

Answer 4

If you're looking to improve the clarity of your code, you might consider using some shorthand techniques. Just make sure that 0 isn't a valid application ID:

const id = result.application._id || 0;
if(!id || applicant_id !== id.toString()){
  // redirect
}

Update: Let me clarify - the || operator in the variable assignment will choose the first truthy value it encounters, or the second one if the first is undefined. So, even if the value defaults to 0, which is falsey, the check will still fail unless you convert it to a string.

Update 2: If your IDs are purely numerical (as they appear to be), there's no need to convert them to strings. Let JavaScript handle coercion for you by using != instead of !==.

const id = result.application._id || 0;
if(!id || applicant_id != id){
 // redirect
}

In JavaScript, 12 == '12' evaluates to true while 12 === '12' evaluates to false. It's generally recommended to use === unless you explicitly want to rely on type coercion, and this situation seems like a good fit for it :)

Answer 5

Answer №3

🏄 Here's a quick solution:

.: NEW VERSION :.

const user = response.user || {}
if (user_id !== `${user._id}`) {
  console.log('redirecting user');
}

Answer 6

🏄 Here's a quick solution:

.: NEW VERSION :.

const user = response.user || {}
if (user_id !== `${user._id}`) {
  console.log('redirecting user');
}

Make sure that when accessing an object, any undefined values do not cause the entire application to break

Answer №1

Answer №2

Answer №3

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