This question already has answers here:
What do multiple arrow functions mean in JavaScript?
(7 answers)
How does the spread syntax in ES6 JS work as a function argument?
(1 answer)
What are these three dots in React doing?
(23 answers)
Closed 5 years ago.
How does this work:
const invert = fn => (...args) => -fn(...args);
Specifically, what is happening with (...args). It behaves as if it is separating the arguments from the function after the first fat arrow, but I suspect there is a better, more specific, explanation. Thanks.
Related
This question already has answers here:
Spread Syntax ES6
(8 answers)
Closed 7 months ago.
I am trying to learn javascript but having trouble in the spread and rest operators.
Can't understand whats happening here how dose this take in the taxRate parameter like a singel number when we spred the itemsBought parameter
function addTaxToPrices (taxRate, ...itemsBought)
{
return(itemsBought.map(item => item*taxRate));
}
let ShoppingCart=addTaxToPrices(1.1,46,89,35,79);
console.log(ShoppingCart)
for my understanding it is nearly the same than if you do:
function addTaxToPrices (taxRate, itemsBought)
{
return(itemsBought.map(item => item*taxRate));
}
itemsBought = [46,89,35,79]
let ShoppingCart=addTaxToPrices(1.1,itemsBought);
console.log(ShoppingCart)
This question already has answers here:
Why doesn't my arrow function return a value?
(1 answer)
Curly Brackets in Arrow Functions
(3 answers)
When should I use a return statement in ES6 arrow functions
(6 answers)
Closed 1 year ago.
The following code works:
let check = checkingImages.every((item)=>item.classList.contains('matched'))
But this one doesn't:
let check = checkingImages.every((item)=>{
item.classList.contains('matched')
})
Can someone explain what's the reason for the second code not working, please?
This question already has answers here:
When should I use a return statement in ES6 arrow functions
(6 answers)
How is () => {...} different from () => [duplicate]
(4 answers)
Arrow function without curly braces
(9 answers)
Are 'Arrow Functions' and 'Functions' equivalent / interchangeable?
(4 answers)
Closed 2 years ago.
This probably suits other methods as well but the one i'm using at the moment is map().
How come:
const singleFruit = fruits.map((fruit) => fruit.toUpperCase());
console.log(singleFruit);
returns the array the correct way, with everything in uppercase, when:
const singleFruit = fruits.map((fruit) => {
fruit.toUpperCase();
});
console.log(singleFruit);
gives me an array but with my assigned fruits are now undefined. I can solve this by adding return before "fruit.toUpperCase();" I thought that the second code was the exact same as the first one but without the curly braces.
Thanks!
This question already has answers here:
Indirect function call in JavaScript
(3 answers)
Why does babel rewrite imported function call to (0, fn)(...)?
(3 answers)
Closed 5 years ago.
onSelect(option, (0, _getOptionText2.default)(option))
I saw this in one of the node modules I use and I'm pretty confused by the second argument which is wrapped by parentheses. How does that work? There is no function which it is invoking.
This question already has answers here:
What's the meaning of "=>" (an arrow formed from equals & greater than) in JavaScript?
(14 answers)
Closed 6 years ago.
Easy question for someone to answer, what happens in this typescript function?
getTweetCount = () => this.data.totalCount;
data.totalCount is of type number from a service.
getTweetCount = () => this.data.totalCount;
You are creating an "arrow function" that returns this.data.totalCount. There are lots of docs about arrow functions out there.
More
Arrow functions are also covered here : https://basarat.gitbooks.io/typescript/content/docs/arrow-functions.html