Question

我有以下js函数：

function Weekday (name, traffic) {
this.name = name;
this.traffic = traffic;
}

function mostDays(){
var traffic=[];
traffic[0] = new Weekday('monday',6);
traffic[1] = new Weekday('tuesday',5);
return traffic;
}

function mostPopularDays(week) {    
if(week.length == 0 || week === null) return null;

return Math.max.apply(Math, week['traffic']);
}

所以，如果我说：

 var x = mostDays();
 var test = mostPopularDays(x);

我正在尝试返回6，这是工作日对象中流量的最大值。有没有办法正确引用它，还是我需要在循环中完成所有这些？

Answer 1

您可以映射对象的所需属性，然后获取最大值。

function Weekday(name, traffic) {
    this.name = name;
    this.traffic = traffic;
}

function mostDays() {
    var traffic = [];
    traffic[0] = new Weekday('monday', 6);
    traffic[1] = new Weekday('tuesday', 5);
    return traffic;
}

function mostPopularDays(week) {
    if (!week.length) return null;
    return Math.max.apply(Math, week.map(function (o) { return o.traffic; }));
}

var x = mostDays();
var test = mostPopularDays(x);

console.log(test);

使用ES6，您可以传播Math.max的值。

function Weekday(name, traffic) {
    this.name = name;
    this.traffic = traffic;
}

function mostDays() {
    return [
        new Weekday('monday', 6),
        new Weekday('tuesday', 5)
    ];
}

function mostPopularDays(week) {
    if (!week.length) return null;
    return Math.max(...week.map(o => o.traffic));
}

var x = mostDays();
var test = mostPopularDays(x);

console.log(test);

Answer 2

如果您想要返回流量最多的日期，那么Math.max无法独立完成，因为它只会返回最高流量（如果您正确编码），而不是当天。

您可以使用find查找流量最高的一天：

var maxTraffic = Math.max(...week.map(day => day.traffic));
return week.find(day => day.traffic === maxTraffic);

Answer 3

另一个选项可以是指定对象的默认valueOf：

function Weekday(name, traffic) {
    this.name = name;
    this.traffic = traffic;
}
Weekday.prototype.valueOf = function() { return this.traffic }

var days = [ new Weekday('monday', 6), new Weekday('tuesday', 5) ]

console.log( Math.max.apply(0, days) )
console.log( Math.max(...days) )

否则，可以使用reduce：

function Weekday(name, traffic) {
    this.name = name;
    this.traffic = traffic;
}

var days = [ new Weekday('monday', 6), new Weekday('tuesday', 5) ]

var max = days.reduce((m, d) => Math.max(m, d.traffic), 0)

console.log(max )

如何在包含数组

3 个答案: