与三元运算符混淆

Question

我想将函数中的 if 语句转换为三元运算符。这个功能是选择任意元素。

function s(el, index, all){
    if(el !== undefined && index === undefined)
        return document.querySelector(el);
    else if(el !== undefined && index !== undefined && all === true)
        return document.querySelectorAll(el);
    else
        return document.querySelectorAll(el)[index];
}

Answer 1

你可以像这样干净利落地做到这一点

function s(el, index, all){
    let firstCondition = el !== undefined && index === undefined;
    let secondCondition = el !== undefined && index !== undefined && all === true;
    return firstCondition ? document.querySelector(el) : secondCondition ? document.querySelectorAll(el) : document.querySelectorAll(el)[index];
}

Answer 2

return (el !== undefined && index === undefined)?document.querySelector(el):(el !== undefined && index !== undefined && all === true)?document.querySelectorAll(el):document.querySelectorAll(el)[index];