javascript检查是否设置了数组键

Question

var place = []

place[0] = "Sant Marti de Canals";
place[1] = "Catalonia";
place[3] = "";
place[4] = "Spain";

placeTitle = place.join(",");

当前输出是“Sant Marti de Canals,Catalonia,,,Spain”

怎么会是“Sant Marti de Canals,Catalonia,Spain”

Answer 1

您还可以定义一个过滤器函数，这在许多其他情况下都很有用。

Array.prototype.filter = function(p) {
    var a = [];
    p = p || function (x) {return x;}
    for (var i = 0; i<this.length; ++i) {
        if (p(this[i])) {
            a.push(this[i]);
        }
    }
    return a;
}

...

placeTitle = place.filter().join(', ');