無法從數組（Javascript）中獲取最小值？

Question

我試圖從數組中獲取最小值，但我遇到了這種奇怪的行為。 我的期望是得到 89 作為最小距離，而不是我得到 100。誰能解釋一下？

// 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

您需要使用數字而不是字符串進行比較。 比較字符串與數字不同。 下面是一些例子：

 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

讓我們將其分解為最小代碼示例。 您正在（恕我直言過度嵌套） nodes對象內的edge數組中尋找屬性distance的最小值。

問題是distance值是字符串，而不是數字。 因此，應將這些值轉換為Number以便能夠比較它們並確定distance值的最小值。 現在使用+[a numeric string value]將距離映射到Number 。

要確定最小值，您可以隨后將Math.min應用於映射的數值數組。

 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

正如羅賓指出的那樣-您正在比較字符串。 如果您無法在數據源中存儲整數，則可以使用parseInt()執行以下操作；

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

Answer 4

將字符串更改為距離對象中的數字。

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