I'm initializing a variable conditionally with if/else. I want to follow functional programming rules.
My eg.:
if (1 === 2) {
const a = false;
} else {
const a = true;
}
console.log(a);
Linter say: ESLint: 'a' is not defined.(no-undef).
As you know there is no way that a would not be defined. Another approach could be:
const a = 1 === 2 ? false : true;
But what if there were three conditions in if/else? How do I achieve that and avoid error?
That's why I always use var. But for your example you can have define const a using a function or a intermediate variable.
const a = init_a()
function init_a() {
if (1 == 2) {
return 1;
} else {
return 2;
}
}
console.log(a)
You need to define your variable in a scope that you can access and print.
You can use something more elegant like this:
const a = (1 ==2) ? 'A' : 'B'
console.log(a)
For more info check What is the scope of variables in JavaScript?
You can use an IIFE (Immediately Invoked Function Expression) if you want to stick to functional programming style.
This is especially useful when dealing with multi-level if and switch statements:
const a = (() => {
if (1 === 1) {
return 'first'
} else if (1 === 2) {
return 'second'
} else {
return 'third'
}
})()
// 'first'
console.log(a)
doStuff(a);