This question already has answers here:
ES6 concise methods and non-concise methods in object literals
(1 answer)
Are 'Arrow Functions' and 'Functions' equivalent / interchangeable?
(4 answers)
Methods in ES6 objects: using arrow functions
(6 answers)
Closed 2 years ago.
I'm still not very familiar with all the ES6 syntax, and I'm starting to learn Vue.js, which makes extensive use of it. So, I find something that puzzles me a bit:
What's the difference between these two methods?
const actions = {
foo1(num) {
console.log(num);
},
foo2: (num) => {
console.log(num);
}
}
actions.foo1(2);
actions.foo2(3);
// output: 2
// output: 3
I guess they are not the same, although they both output their passed value.
Related
This question already has answers here:
What does "this" refer to in arrow functions in ES6?
(10 answers)
Methods in ES6 objects: using arrow functions
(6 answers)
Are 'Arrow Functions' and 'Functions' equivalent / interchangeable?
(4 answers)
Closed 8 months ago.
i just created an object with an arrow function :
const user={
fName:"0xN1nja",
about:()=>{
return this.fName;
}
}
now, when i call that arrow function with .call() method, it returns undefined :
a=user.about.call(user);
console.log(a);
>>> undefined
But when i replaced that arrow function with a normal function expression, it returns the value
const user={
fName:"0xN1nja",
about:function(){
return this.fName;
}
}
a=user.about.call(user2);
console.log(a);
>>> 0xN1nja
what is happening here?
PS : im new to javascript
Arrow functions don't bind to this as function do. That's one of the main reason they were introduced (probably the most important one).
You cannot even bind them.
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:
Methods in ES6 objects: using arrow functions
(6 answers)
Are 'Arrow Functions' and 'Functions' equivalent / interchangeable?
(4 answers)
Closed 4 years ago.
i have this object literal
let p = {
name : 'Amir',
say: () => {
console.log(this.name)
console.log(this)
}
}
and I want the say function works using this
p.say();
but the arrow function obviously gets the window object as 'this'. I know I could use a regular function for 'say' instead of arrow and it will work fine.
BUT
I would like to ONLY change the call to say function to make it work, but the binding won't work.
I mean something like p.say.bind(p)() or p.say.call(p) aint gonna work as desired.
Is it possible to change the call to function ONLY and not the say function?
This question already has answers here:
Are 'Arrow Functions' and 'Functions' equivalent / interchangeable?
(4 answers)
Methods in ES6 objects: using arrow functions
(6 answers)
Closed 4 years ago.
Can't find this info anywhere on the web. Is there any difference (e.g. in performance) between these two methods created with object literal syntax? Or is the mechanism under the hood exactly the same?
let test = {
foo(){
console.log("foo");
return 1;
},
bar: () => {
console.log("bar");
}
}
console.log(test.foo());
console.log(test.bar());
There shouldn't be any performance difference -- the shorthand function property is just syntactic sugar.
However, there's an operational difference. The shorthand notation is short for the traditional function syntax, not an arrow function. So it's equivalent to:
foo: function() {
console.log("foo");
}
Arrow functions have a number of different behaviors from traditional function expressions. See Arrow function vs function declaration / expressions: Are they equivalent / exchangeable?
Your example functions don't do anything that depends on the differences, but in a real application they might.
This question already has answers here:
Are 'Arrow Functions' and 'Functions' equivalent / interchangeable?
(4 answers)
Using arrow functions with .call()? "This" varies based on if in devtools or iojs locally? Should one avoid using arrows with .call?
(1 answer)
Can you bind 'this' in an arrow function?
(14 answers)
Closed 5 years ago.
I know about using .call() and .apply() to set the this for a function call, but can I use it for a lambda?
Consider this example from the MDN webdoc for Function.prototype.call:
function greet1() {
var reply = [this.person, 'Is An Awesome', this.role].join(' ');
console.log(reply);
}
let greet2 = () => {
var reply = [this.person, 'Is An Awesome', this.role].join(' ');
console.log(reply);
}
var i = {
person: 'Douglas Crockford', role: 'Javascript Developer'
};
greet1.call(i); // Douglas Crockford Is An Awesome Javascript Developer
greet2.call(i); // Is An Awesome Javascript Developer
Why doesn't the greet2 call work the same was as greet1 and is there a way to set this in the case of greet2?