// Write-only variables are not considered as used.
let y = 10;
y = 5;

// A variable that modifies only itself isn't considered used.
let z = 0;
z = z + 1;

// Unused argument
(function(x) {
    return 5;
})();

// Unused recursive functions also raise this issue.
function fact(n) {
    if (n < 2) return 1;
    return n * fact(n - 1);
}

// When a function definition destructures an array,
// unused entries from the array also cause warnings.
function getY([x, y]) {
    return y;
}

let x = 10;
alert(x);

((arg1) => {
    return arg1;
})();

let myFunc;
myFunc = (n) => {
    // this is legal
    if (n < 0) myFunc();
};

// this is also considered legal
console.log(declaredLater);
var declaredLater;

// Only the second argument from the descructured array is used.
function getY([, y]) {
    return y;
}