Meteor Stripe Package Mrgalaxy Cannot Read Property Stripe of Undefined
Ane of the most common type errors in JavaScript is the famous "Cannot read property of undefined". This error occurs when y'all try to read or access a property on an object that is undefined. Another common instance that is caused past a like issue, is when y'all get the aforementioned error message, but with null instead of undefined.
Cannot read property of null
Why does this happen?
Imagine the post-obit situation. Y'all take a user object that is initially undefined, and it is populated through a fetch request. Your server is down and so it returns with an undefined value, but you didn't handle this failure path, and you even so effort to read backdrop from the user object:
let user; // The variable is set to undefined user = look getUser (id) ; // The request fails and returns `undefined`, simply it is not handled panel. log (user.name) ; // Y'all try to log the `name` property of the `user` object, that is still `undefined` Copied to clipboard!
The variable in the lawmaking example above is declared, but its value is still set to undefined. Here you are essentially trying to do the post-obit:
panel. log ( undefined .name) ; // This volition throw "Cannot read property 'name' of undefined" // Same as if the asking returns with a `null` and yous try to read properties from that console. log ( null .proper name) ; // This will throw "Cannot read holding 'name' of null" Copied to clipboard!
Since undefined is non an object, yous will get a TypeError, like the 1 beneath. Then how can we avoid this?
Fugitive errors
To avoid getting these types of errors, we need to make sure that the variables we are trying to read exercise have the correct value. This can exist done in various ways. Nosotros can practice if checks before dealing with objects whose values are bound to alter:
if (user !== undefined ) { // Here `user` is surely not `undefined` } if ( typeof (user) !== 'undefined' ) { // We can too utilize the `typeof` operator } Copied to clipboard!
A much cleaner solution however is to apply the logical OR operator, when you assign a value to a variable, or even better, when you return the value from the function:
// Assign a fallback during declaration user = getUser (id) || { } ; // Assign a fallback during render const getUser = id => { ... return userResponse || { } ; } ; Copied to clipboard!
If getUser returns undefined or null, so we can fall back to an empty object, and assign that to the user variable. This way, if nosotros try to access user.name, we volition get undefined, as nosotros don't have that property on the user object, but we still have an object to work with, so we don't become an mistake. We can too use TypeScript to easily spot these types of mistakes correct within our IDE.
Resources:
- Logical OR operator
- The
typeofoperator
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Source: https://www.webtips.dev/webtips/javascript/avoid-getting-cannot-read-property-of-undefined-in-javascript
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