What the ideologically better for JavaScript?

check_then_throw_error.js

function onlyStringArgument(string) {
    if (typeof string !== "string") {
        throw new Error('string must be a string');
    }
    return string.split(';');
}

onlyStringArgument(42);

fix_type.js

function onlyStringArgument(string) {
    return String(string).split(';');
}

onlyStringArgument(42);

let_throw_error.js

function onlyStringArgument(string) {
    return string.split(';');
}

onlyStringArgument(42);