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This has two benefits: (1) It is less awkward to write function foo(){} than const foo = () => {} — in particular outside other function calls. (2) The function name shows in stack traces. While it would be tedious to name every internal callback, naming all the public functions is probably a good idea.
1. this will always refer to the global object when used inside an arrow function. Use the regular function declaration to refer to the local object. Also, you can use the object name as the context (object.method, not this.method) for it to refer to the local object instead of the global (window).
These are Arrow Functions. Also known as Fat Arrow Functions. They're a clean and consise way to write function expressions, e.g. function() {}. Arrow Functions can remove the need of function, return and {} when defining functions. They are one-liners, similar to Lambda Expressions in Java or Python. Example with no parameters
Longer answer: Arrow functions do not have this, arguments or other special names bound at all - when the object is being created the name this is found in the enclosing scope, not the person object. You can see this more clearly by moving the declaration: var person = {. name: "Jason". }; person.shout = () => console.log("Hi, my name is", this);
you can use: ary.forEach(i=>callback); But you'd better use arrow function in this way,and there is no need to define function callback. let ary = [1,2,3,4,5]; ary.forEach(i=>{. console.log(i); }); Arrow functions like anonymous functions. That's an array function,and i is the param.
Instead, as outlined by @BenAston, there are differences about the instantiation of the function and the context (e.g. with arrow functions this doesn't change context). About readability it's also habit. Arrow functions seem more complicated to read, but also because we are used to read them in the older way. Also readability it's a point of view.
Using async method inside of a class: // do something. The OP appears to be looking for a named, async, arrow function which is the one syntax you do not show. Actually, const foo = async () => {} creates a named async function named foo. It's entirely possible to do named functions this way (just no hoisting).
From 'Arrow functions' on MDN: An arrow function expression has a shorter syntax compared to function expressions and lexically binds the this value. Arrow functions are always anonymous. This is particularly pertinent in your example considering that it is taken from a reactjs application.
You have give in your answer two separate point of views: 1. is an implicit return equivalent to => { return ()} 2. ( only serves to disambiguate between the start of an object and the opening braces of a function body. @TomFenech That's not fully correct either. There is only an implicit return when it's single line.
Arrow functions and function declarations / expressions are not equivalent and cannot be replaced blindly. If the function you want to replace does not use this, arguments and is not called with new, then yes. As so often: it depends. Arrow functions have different behavior than function declarations / expressions, so let's have a look at the ...