Converting Typescript fat arrow syntax to regular Javascript syntax

Question

Converting Typescript fat arrow syntax to regular Javascript syntax

I recently started learning typescript and I'm having trouble understanding the => arrow function. Could someone clarify the meaning of this JavaScript code snippet for me:

this.dropDownFilter = values => values.filter(option => option.value !== 'Others')

angular typescript

Answer 1

Answer №1

When arrow functions are not used in a special way to handle scope, the code would look like this:

this.dropDownFilter = function(values){
  return values.filter(function(option){ return option.value !== 'Others' })
}

Answer 2

When arrow functions are not used in a special way to handle scope, the code would look like this:

this.dropDownFilter = function(values){
  return values.filter(function(option){ return option.value !== 'Others' })
}

Answer 3

Answer №2

When exploring the documentation for the fat arrow syntax, you will come across various examples such as:

arg => console.log(arg); // <-- () not necessary for single argument
(a, b) => console.log(a,b); // <-- () required for multiple arguments
arg => { return arg; } // <-- includes a return statement within {}
(a, b) => { return a+b; } // <-- includes a return statement within {}

this.dropDownFilter = values => values.filter(option => option.value !== 'Others')

One key advantage is that it inherently incorporates lexical this. Therefore, there is no need to store this in a variable to utilize it within the function.

This can be likened to:

this.dropDownFilter = function(values) {
  return values.filter(function(option) {
    return option.value !== 'Others'
  })
}

If we analyze further:

The assignment of an anonymous function with the argument values to this.dropDownFilter.
The fat arrow syntax features an implicit return statement.
The inner .filter() method contains an anonymous function responsible for returning the filtered value.

Answer 4

When exploring the documentation for the fat arrow syntax, you will come across various examples such as:

arg => console.log(arg); // <-- () not necessary for single argument
(a, b) => console.log(a,b); // <-- () required for multiple arguments
arg => { return arg; } // <-- includes a return statement within {}
(a, b) => { return a+b; } // <-- includes a return statement within {}

this.dropDownFilter = values => values.filter(option => option.value !== 'Others')

One key advantage is that it inherently incorporates lexical this. Therefore, there is no need to store this in a variable to utilize it within the function.

This can be likened to:

this.dropDownFilter = function(values) {
  return values.filter(function(option) {
    return option.value !== 'Others'
  })
}

If we analyze further:

The assignment of an anonymous function with the argument values to this.dropDownFilter.
The fat arrow syntax features an implicit return statement.
The inner .filter() method contains an anonymous function responsible for returning the filtered value.

Answer 5

Answer №3

This code snippet illustrates the syntax for defining a function in JavaScript, where the arguments are placed to the left of =>, and the function body is on the right of =>. Two important points to note:

Arguments are typically enclosed in parentheses similar to traditional function syntax, but when there's only one argument, the parentheses are optional.
When an arrow function consists of just one statement (as in the provided code snippet), that statement serves as the implicit return statement. For multiple statements, the function body must be wrapped in curly braces and include an explicit return keyword.

For instance:

function myFunc (arg1) {
  return arg1
}

is the same as:

var myFunc = arg1 => arg1

and also equivalent to:

var myFunc = (arg1) => {
  return arg1
}

There are additional considerations such as the context of this (which behaves differently in arrow functions) and the lack of support for the arguments keyword in arrow functions. For further details, you can refer to MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

Answer 6

This code snippet illustrates the syntax for defining a function in JavaScript, where the arguments are placed to the left of =>, and the function body is on the right of =>. Two important points to note:

Arguments are typically enclosed in parentheses similar to traditional function syntax, but when there's only one argument, the parentheses are optional.
When an arrow function consists of just one statement (as in the provided code snippet), that statement serves as the implicit return statement. For multiple statements, the function body must be wrapped in curly braces and include an explicit return keyword.

For instance:

function myFunc (arg1) {
  return arg1
}

is the same as:

var myFunc = arg1 => arg1

and also equivalent to:

var myFunc = (arg1) => {
  return arg1
}

There are additional considerations such as the context of this (which behaves differently in arrow functions) and the lack of support for the arguments keyword in arrow functions. For further details, you can refer to MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

Converting Typescript fat arrow syntax to regular Javascript syntax

Answer №1

Answer №2

Answer №3

Similar questions

When utilizing custom ngDoBootstrap and createCustomElement in Angular, the router fails to recognize the URL being used

A Typescript function will only return a partial if the parameter passed into it is also

What is the best way to compile TypeScript files without them being dependent on each other?

Error message "Angular build with --prod causes Uncaught TypeError: e is not a constructor when running ng serve"

Issues with utilizing destructuring on props within React JS storybooks

Injecting dynamic templates in Angular 7

The FullCalendarModule does not have a property named 'registerPlugins' in its type definition

Error in Typescript: The property 'children' is not included in the type but is necessary in the 'CommonProps' type definition

I am having trouble getting my angular image to switch using angular animations

Utilize the up and down arrow keys to scroll through a description list in React

How do you properly include a new property in an Object using Typescript?

After executing a query to a PostgreSQL database, I encountered an error preventing me from using res.send(). The error message stated: "Cannot set headers after they are sent to the client."

Utilizing PrimeNG dropdowns within various p-tree nodes: Distinguishing between selected choices

VSCode displaying HTML errors within a .ts file

Encountered a problem with loading external SCSS files in style.scss using Angular CLI 6 due to issues with postcss-loader and raw-loader in node_modules

Encountering a Typescript issue when linking a class component with the reducer

How to Add RouterModule to an Angular 10 Library without Ivy

Error occurs with navctrl when using jquery in Ionic 3

Mistakes following update to Angular 4 from Angular 2

Gather keyboard information continuously