I have a function 'sometimes' and want to return a function object from it.
Below is my code:
let add = (a, b) => {
return a + b;
};
myFunc = sometimes(add);
const outputArr = [];
for (let i = 0; i < 3; i++) {
outputArr.push(myFunc(2 + i, 3 + i));
}
function sometimes (inputFunc){
return function (a, b){
return inputFunc()
}
}
outputArr
I expect my outputArr variable to equal:
[5, 7, 9]
Instead mine equals:
[ NaN, NaN, NaN ]
What am I doing wrong?
You are not passing the parameters to the wrapped function. The add function tries to sum two undefined values and the result is NaN (not a number).
You have to pass the parameters to the wrapped function:
return function(a, b) {
return inputFunc(a, b); // <<<
}
Since sometimes is a higher order function, that needs to wrap different functions, with a changing number of parameters, it can't know the implementation of the wrapped function. To ensure that, you should use rest parameters (to collect the parameters to an array) and spread (to convert the array back to parameters) to pass the arguments to the wrapped function.
let add = (a, b) => {
return a + b;
};
myFunc = sometimes(add);
const outputArr = [];
for (let i = 0; i < 3; i++) {
outputArr.push(myFunc(2 + i, 3 + i));
}
function sometimes(inputFunc) {
return function(...args) {
return inputFunc(...args)
}
}
console.log(outputArr);
you can use your code as
function sometimes(a,b){
return a + b;
}
const outputArr = [];
for (let i = 0; i < 3; i++) {
outputArr.push(sometimes(2 + i, 3 + i));
}
console.log(outputArr);
now the output is
[ 5, 7, 9 ]
return inputFunc(a, b)