javascript - 在 .map 中添加条件
问题描述
这是我想从列表中随机选择一个城市的代码,根据它的权重,然后根据城市之间的距离修改权重(选择城市的距离越大,权重越大)。在此之后,我再次使用修改后的列表随机选择另一个城市。代码工作正常,除了一件事......
这是代码:
// list of cities
var liste = [
{ name: "New York", distance: 12, weight: 5},
{ name: "Atlanta", distance: 4, weight: 4},
{ name: "Dallas", distance: 2, weight: 2},
{ name: "Los Angeles", distance: 1, weight: 1},
];;
var repeatTimes = 4;
var choose = [];
choose = [liste.map(x=>x.name), liste.map(x=>x.distance), liste.map(x=>x.weight)];
// randomaly pick a city based on its weight
var rand = function(min, max) {
return Math.random() * (max - min) + min;
};
var getRandomItem = function(choose, weight) {
var total_weight = weight.reduce(function (prev, cur, i, arr) {
return prev + cur;
});
var random_num = rand(0, total_weight);
var weight_sum = 0;
//console.log(random_num)
for (var i = 0; i < choose.length; i++) {
weight_sum += weight[i];
weight_sum = +weight_sum.toFixed(2);
if (random_num <= weight_sum) {
return choose[i];
}
}
// end of function, modify the weights of list again
};
// for the first time pick a city randomaly
var random_item = getRandomItem(choose[0], choose[2]);
console.log(random_item);
newWeights();
// after the first time of picking cities let's modify the weights of list
function newWeights(){
var baseDistance = liste.find(l => l.name == random_item).distance;
console.log(choose[0].indexOf(random_item));
var list = liste.map(c => {
var newWeight = Math.abs(baseDistance - c.distance);
return {
name: c.name,
distance: c.distance,
weight: newWeight
};
});
liste = list.filter(function(value){
return value.weight != 0;
});
choose = [liste.map(x=>x.name), liste.map(x=>x.distance), liste.map(x=>x.weight)];
console.log(liste);
}
// use the modified list to randomaly picking another city
for (var i = 1; i < repeatTimes; i++) {
var random_item = getRandomItem(choose[0], choose[2]);
console.log(random_item);
newWeights();
}
//
这是我创建包含修改后的列表的列表数组的地方。
var list = liste.map(c => {
var newWeight = Math.abs(baseDistance - c.distance);
return {
name: c.name,
distance: c.distance,
weight: newWeight
};
});
我想要的只是将每个对象的权重添加到newWeight中,如下所示:
if(newWeight !== 0){
var newWeight = Math.abs(baseDistance - c.distance) + c.weight;
}
但每次我得到错误。
解决方案
在您的 newWeights 方法中,您重新分配了一个新值以列出...
看看这个:https ://jsfiddle.net/gbc9w06y/
// list of cities
var liste = [
{ name: "New York", distance: 8, weight: 1 },
{ name: "Atlanta", distance: 4, weight: 1 },
{ name: "Dallas", distance: 2, weight: 1 },
{ name: "Los Angeles", distance: 1, weight: 1 },
];
var repeatTimes = 4;
var choose = [];
choose = [liste.map(x=>x.name), liste.map(x=>x.distance), liste.map(x=>x.weight)];
// randomaly pick a city based on its weight
var rand = function(min, max) {
return Math.random() * (max - min) + min;
};
var getRandomItem = function(choose, weight) {
var total_weight = weight.reduce(function (prev, cur, i, arr) {
return prev + cur;
});
var random_num = rand(0, total_weight);
var weight_sum = 0;
//console.log(random_num)
for (var i = 0; i < choose.length; i++) {
weight_sum += weight[i];
weight_sum = +weight_sum.toFixed(2);
if (random_num <= weight_sum) {
return choose[i];
}
}
// end of function, modify the weights of list again
newWeights();
};
// for the first time pick a city randomaly
var random_item = getRandomItem(choose[0], choose[2]);
console.log(random_item);
newWeights();
// after the first time of picking cities let's modify the weights of list
function newWeights(){
var baseDistance = liste.find(l => l.name == random_item).distance;
var list = liste.map(c => {
console.log();
var newWeight = Math.abs(baseDistance - c.distance);
return {
name: c.name,
distance: c.distance,
weight: newWeight
};
});
liste = list;
choose = [liste.map(x=>x.name), liste.map(x=>x.distance), liste.map(x=>x.weight)];
console.log(list);
}
// use the modified list to randomaly picking another city
for (var i = 1; i < repeatTimes; i++) {
var random_item = getRandomItem(choose[0], choose[2]);
console.log(random_item);
}
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