Cannot get minimum value from Array (Javascript)?

Question

I'm trying to get the minimum value from an Array, and i come across this weird behavior. My expectation is to get 89 as the minimumDistance, instead i get 100. Can anyone explain this ?

// 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 );

Is there some other reason you are storing these numeric properties as strings rather than numbers? The cause of the problem is that you're sorting strings, not numbers - you could fix it by altering the line that does the comparison, but you'll likely cause yourself fewer headaches by just changing the data to use numbers. — Robin Zigmond
– Robin Zigmond, Commented Nov 24, 2019 at 9:36
Welcome to StackOverflow! It can help a lot if you quickly learn how to debug program code. — Jeroen Heier
– Jeroen Heier, Commented Nov 24, 2019 at 9:36
@RobinZigmond No particular reason, the array is actually json and much bigger in length. — TheOldWarrior
– TheOldWarrior, Commented Nov 24, 2019 at 9:50

Kenma · Accepted Answer · 2019-11-24 09:54:25Z

2

You need to take a number instead of a string for comparing. Comparing string is different from numbers. Here is some example:

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 );

edited Nov 24, 2019 at 9:54

Kenma

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answered Nov 24, 2019 at 9:35

Nina Scholz

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1 Comment

Aabhushan Gautam Over a year ago

didn't know +would change a string tto a number. great answer.

KooiInc · Accepted Answer · 2019-11-24 11:20:58Z

Let's break this down to a minimum code example. You are looking for the minimum value of the property distance within the edge array within your (imho overly nested) nodes object.

Problem is that the distance values are strings, not numbers. So, the values should be converted to Number to be able to compare them and determine the minimum of the distance values. Now the distances are mapped to Number by using +[a numeric string value].

To determine the minimum value you can subsequently apply Math.min to the mapped array of numeric values.

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);

Ludo · Accepted Answer · 2019-11-24 09:38:28Z

0

As Robin pointed out - you're comparing strings. If you can't store integers in your data source, you can do the following with parseInt();

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

answered Nov 24, 2019 at 9:38

Ludo

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Comments

Aabhushan Gautam · Accepted Answer · 2019-11-24 09:40:14Z

0

Change the strings to numbers in distance object.

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

answered Nov 24, 2019 at 9:40

Aabhushan Gautam

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