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javascriptarrays
Syed Ariff
Syed Ariff

Reputation: 732

How to set the value of a property in an array of objects to be in reverse?

I have an array of objects called thresholds :

thresholds: [{
                dType: "threshold",
                from: 0,
                to: 30,
                color: "#D91427"
            },
            {
                dType: "threshold",
                from: 30,
                to: 70,
                color: "#F2910A"
            },
            {
                dType: "threshold",
                from: 70,
                to: 120,
                color: "#219131"
            }
            ]

How do I set the color property of each object in reverse? For example , something like this , 

thresholds: [{
                dType: "threshold",
                from: 0,
                to: 30,
                color: "#219131"
            },
            {
                dType: "threshold",
                from: 30,
                to: 70,
                color: "#F2910A"
            },
            {
                dType: "threshold",
                from: 70,
                to: 120,
                color: "#D91427"
            }
            ]

Upvotes: 1

Views: 58

Answers (3)

Harshith Rai
Harshith Rai

Reputation: 3066

It is simple Ariff, just loop through the thresholds array. Calculate the total length of the array, and loop through the half of it, swapping the color values of objects inside the thresholds[] which correspond to each other on opposite ends, for example, 1st element -- last element, 2nd element -- 2nd element from last, and so on...

Here is the code snippet. I hope it helps.

var thresh_len = thresholds.length-1;
for(var i = 0; i < (thresh_len/2); i++) {
    var temp = thresholds[i].color;
    thresholds[i].color = thresholds[(thresh_len - i)].color;
    thresholds[(thresh_len - i)].color = temp;
}

Upvotes: 1

Dathan
Dathan

Reputation: 4553

  • Pass array of colors
  • Refer to that array in the object
  • Use the reverse() property of Array to reverse the array, so that the reference is also reversed

getThresholds(colors) {
  return [{
    dType: "threshold",
    from: 0,
    to: 30,
    color: colors[0]
  },
  {
    dType: "threshold",
    from: 30,
    to: 70,
    color: colors[1]
  },
  {
    dType: "threshold",
    from: 70,
    to: 120,
    color: colors[2]
  }]
}

const colors = ["#219131", "#F2910A", "#D91427"]

thresholds : getThresholds(colors)

thresholds : getThresholds(colors.reverse())

Upvotes: 0

Cid
Cid

Reputation: 15247

I'd loop from 0 to (len - 1) / 2 and swap each color

let thresholds = [{
                dType: "threshold",
                from: 0,
                to: 30,
                color: "#D91427"
            },
            {
                dType: "threshold",
                from: 30,
                to: 70,
                color: "#F2910A"
            },
            {
                dType: "threshold",
                from: 70,
                to: 120,
                color: "#219131"
            }
            ];

function swap(obj, i, len)
{
  let temp = obj[i].color;
  obj[i].color = obj[len - 1 - i].color;
  obj[len - 1 - i].color = temp;
}

let arrayLen = thresholds.length;

for (let i = 0; i <= Math.floor((arrayLen - 1) / 2); ++i)
{
    swap(thresholds, i, arrayLen);
}

console.log(thresholds);

Upvotes: 0

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