An effective method for excluding null values with an Angular pipe

Question

An effective method for excluding null values with an Angular pipe

I am currently working on an Angular pipe that filters results based on user input. The problem I'm encountering is that some of the results do not have a value, resulting in this error message:

Cannot read property 'toLocaleLowerCase' of null

Below is the code for my pipe:

transform(value: QueuedTemplateDto[], filterBy: string): QueuedTemplateDto[] {
    filterBy = filterBy ? filterBy.toLocaleLowerCase() : null;
    return filterBy 
        ? value.filter((check: QueuedTemplateDto) => check.user.toLocaleLowerCase().indexOf(filterBy) !== -1) 
        : value;
}

I attempted to add an if statement to only run the code if the check.user attribute is not null, but encountered errors every time I tried to implement it.

My knowledge of JavaScript is limited in this area. I would greatly appreciate any assistance!

javascript angular typescript

Answer 1

Answer №1

To ensure that the user property is defined, you should check if it's not equal to null. Therefore, include check.user !== null before applying your filter statement (to ignore all falsy values, simply use check.user).

transform(value: QueuedTemplateDto[], filterBy: string): QueuedTemplateDto[] {
filterBy = filterBy ? filterBy.toLocaleLowerCase() : null;
return filterBy ? value.filter((check: QueuedTemplateDto) =>
  check.user !== null && check.user.toLocaleLowerCase().indexOf(filterBy) !== -1) : value;}
  //^^^^^^^^^^^^^^^^^^^^^ ----- here

Note : You have the flexibility to adjust the condition based on your specific needs.

Answer 2

To ensure that the user property is defined, you should check if it's not equal to null. Therefore, include check.user !== null before applying your filter statement (to ignore all falsy values, simply use check.user).

transform(value: QueuedTemplateDto[], filterBy: string): QueuedTemplateDto[] {
filterBy = filterBy ? filterBy.toLocaleLowerCase() : null;
return filterBy ? value.filter((check: QueuedTemplateDto) =>
  check.user !== null && check.user.toLocaleLowerCase().indexOf(filterBy) !== -1) : value;}
  //^^^^^^^^^^^^^^^^^^^^^ ----- here

Note : You have the flexibility to adjust the condition based on your specific needs.

Answer 3

Answer №2

Optimize your JavaScript code by utilizing the truthy/falsy nature of values:

transform(value: QueuedTemplateDto[], filterBy: string): QueuedTemplateDto[] {
  return filterBy && 
    value.filter(item => item && 
      item.user && 
      item.user.toLocaleLowerCase().indexOf(filterBy) !== -1) 
    || value;
}

Understanding this concept is crucial, known as the truthy/falsy values or the holy trinity of Javascript.

Take a look at how it functions:

const empty = '';
const undef = undefined;
const nul = null;
const defined = 'This is defined';
const zero = 0;

const data = ['This is data'];

console.log(empty && data || 'it is empty');
console.log(undef && data || 'it is undefined');
console.log(nul && data || 'it is null');
console.log(nul && data || 'it is equal to zero');
console.log(defined && data || 'You will not see this message');

Answer 4

Optimize your JavaScript code by utilizing the truthy/falsy nature of values:

transform(value: QueuedTemplateDto[], filterBy: string): QueuedTemplateDto[] {
  return filterBy && 
    value.filter(item => item && 
      item.user && 
      item.user.toLocaleLowerCase().indexOf(filterBy) !== -1) 
    || value;
}

Understanding this concept is crucial, known as the truthy/falsy values or the holy trinity of Javascript.

Take a look at how it functions:

const empty = '';
const undef = undefined;
const nul = null;
const defined = 'This is defined';
const zero = 0;

const data = ['This is data'];

console.log(empty && data || 'it is empty');
console.log(undef && data || 'it is undefined');
console.log(nul && data || 'it is null');
console.log(nul && data || 'it is equal to zero');
console.log(defined && data || 'You will not see this message');

An effective method for excluding null values with an Angular pipe

Answer №1

Answer №2

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