javascript - 如何循环遍历数组对象并检查每个元素以查看是否已定义？

Question

我有一个如下所示的数组对象:

var myArr = [undefined, undefined, undefined, undefined, undefined];

如何循环遍历数组对象并调用函数(如果有)数组中的元素已定义且不为 null？

Answer 1

如果您不关心有效值是多少:

var myFunction = function(){console.log("array has valid values");};
var myArr = [undefined, undefined, undefined, undefined, 2];
var hasUndefined = myArr.some(function(item){
    return typeof item !== "undefined";
});
if (hasUndefined){
    myFunction();
}

如果您需要找出有效的项目是什么:

var myFunction = function(validItems){
    console.log("array has valid values, and here they are:",validItems);
};
var myArr = [undefined, undefined, undefined, undefined, 2];
var validItems = myArr.filter(function(item){return typeof item !== "undefined";})
if (validItems.length){
    myFunction(validItems);
}