Where does the below function get parameters from?

user_7551481 0
Viewed 132

Function getFunc is not passed a parameter, why is this code working ?

function getFunc() {
    const a = 7;

    return b => {
        console.log(a+b);
    } }

const f = getFunc();

f(5); //12
function javascript
3 Answers

getFunc returns the anonymous function 

b =>{
  console.log(a+b);
}

so when you make a call to getFunc you're really calling console.log(7+parameter)

user_65348800

It's called closure.

In JavaScript, the code inside functions has access to the variables defined inside this function and to variables defined in all parent functions. If you refer to a variable in the child function that's defined in the parent function and then you return child function JavaScript will preserve variables from the parent functions and they will be available in returned functions.

In your example, you're returning child function 

b => {
    console.log(a+b);
}

from getFunc function so child function still has access to the variable a defined in parent function. When you execute f(5) child function executes 7 + 5 expression and you get 12 in the console.

user_39212530 
function getFunc() {
const a = 7;

return function(b) { //it is more clear syntax
    console.log(a+b);
} }

const f = getFunc(); // here we have a function wich get 'b' parameter

f(5); //here we call this function and pass 5 as a 'b' parameter
user_59074120
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