无法从数组(Javascript)获取最小值？

Question

我试图从一个数组中获取最小值，我遇到了这个奇怪的行为。我的期望是得到89作为minimumDistance，而不是我得到100。有人能解释这个吗？

// List 

var nodes = {
    "node": [
      {
        "name": "test",
        "id": "2",
        "edges": {
          "edge": [
            {
              "to": "4",
              "distance": "89"
            },
            {
              "to": "6",
              "distance": "100"
            },
            {
              "to": "8",
              "distance": "500"
            }
          ]
        }
      }]
}

// Initialization
startNode = 0
currentNode = startNode;


edge = nodes.node[currentNode].edges.edge;
var minimumDistance = 99999;

// Loop through the Neighbors of one Node
for (x= 0; x<edge.length; x++) {
  if (edge[x].distance < minimumDistance) {
      minimumDistance = edge[x].distance;
      } 
  document.write('Neighbor: ' + edge[x].to + ', Distance: ' + edge[x].distance);
  document.write('</br>');
}
 document.write('</br>');
document.write('Minimum Distance: ' + minimumDistance );

Answer 1

为了进行比较，您需要接受一个数字而不是一个字符串。比较字符串与数字不同。下面是一些示例：

​

var nodes = { node: [{ name: "test", id: "2", edges: { edge: [{ to: "4", distance: "89" }, { to: "6", distance: "100" }, { to: "8", distance: "500" }] } }] },
    startNode = 0,
    currentNode = startNode,
    edge = nodes.node[currentNode].edges.edge,
    minimumDistance = Infinity, // greatest value
    x;

for (x = 0; x < edge.length; x++) {
    if (+edge[x].distance < minimumDistance) { // unary plus for getting a number
        minimumDistance = edge[x].distance;
    } 
    document.write('Neighbor: ' + edge[x].to + ', Distance: ' + edge[x].distance);
    document.write('</br>');
}
document.write('</br>');
document.write('Minimum Distance: ' + minimumDistance );

​

Answer 2

让我们将其分解为一个最小的代码示例。您要在(imho覆盖嵌套的) nodes对象的edge数组中寻找属性distance的最小值。

问题是distance值是字符串，而不是数字。因此，应该将这些值转换为Number，以便能够对它们进行比较并确定distance值中的最小值。现在，使用+[a numeric string value]将距离映射到Number。

要确定最小值，可以随后对映射的数值数组应用Math.min。

​

const edge =  [
      {
        "to": "4",
        "distance": "89"
      },
      {
        "to": "6",
        "distance": "100"
      },
      {
        "to": "8",
        "distance": "500"
      }
];
// map distances to numeric values
const distancesFromEdge = edge.map( val => +val.distance );
// determine the minimum value of the mapped values
const minDistance = Math.min.apply(null, distancesFromEdge);
console.log(minDistance);

​

Answer 3

正如Robin所指出的--你是在比较字符串。如果不能在数据源中存储整数，可以使用parseInt()执行以下操作；

if (parseInt(edge[x].distance) < minimumDistance) {
      minimumDistance = parseInt(edge[x].distance);
      }