How to insert a object in an array (as a element )

Question

I am from C++ background. I am trying to translate a C++ code to JavaScript.

in C++ we have vector < pair < int,int > > to store pairs.

in JS i have a situation. i want to store 2D coordinates. i actually want to push new coordinates to the array.

i did like

1. first I created a Object

const coordinate = {
   x= 9,
   y= 10
}

2. Then i tried to push that object into the array CoordinateStorage that i want this object to get stored

CoordinatesStorage.unshift({X : coordinate.x, Y : coordinates.y});

I know this code shown above is absolutely wrong to store an object into the array. I searched out for sources but i got nothing useful. Please recommend some sources that i can refer for such translation related problems if possible.

Answer 1

First initialize the array

var CoordinatesStorage = [];

//create object
const coordinate = {
   x: 9,  // Note - the operator is colon : not = as in the question
   y: 10
}

// push to array
CoordinatesStorage.push(coordinate);

Now your array will be like this [{x:9, y:10}] if you push again the array will be [{x:9, y:10}, {x:9, y:10}]

Tip: Arrays are denoted by square brackets eg: ['math', 'science', 'english']

Objects are denoted by key-value pairs wrapped in curly brackets

eg:  var student = {
                      name: "John", // string value
                      age: 6, // integer value
                      sex: "M",
                      phone: [123456789 , 564654654] // value is of array of 2 items
                   }  

Answer 2

Generally speaking, we should use the .push method for an array. There are other methods available you can find them here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array but the .push method for your case is more suitable.

Basically, as a result, we want to have something like this: [ {x: 2, y: 4 }, { x: 2, y: 4 } ] We have an array of objects.

Or we could also have an array of arrays: [[1, 2], [3, 4], [4, 6]] Not sure if it okay for your case, but maybe as an option.

Also, we could create a class Vector and we might have something like [ Vector { x: 1, y: 2 }, Vector { x: 3, y: 4 }, Vector { x: 4, y: 6 } ]

Let's take a look at the examples:

1. Using the plain object for the vector:

    const coordinate1 = {
      x: 2,
      y: 4
    };
    const coordinate2 = {
      x: 3,
      y: 4
    };

    const coordinatesStorage = [];
    coordinatesStorage.push(coordinate1);
    coordinatesStorage.push(coordinate2);

If you will do console.log(coordinatesStorage) you will see [ { x: 2, y: 4 }, { x: 3, y: 4 } ]

2. Using the array to store a vector:

    const coordinate1 = [1, 2];
    const coordinate2 = [3, 4];
    const coordinatesStorage = [];
    coordinatesStorage.push(coordinate1);
    coordinatesStorage.push(coordinate2);

The coordinatesStorage will be [ [ 1, 2 ], [ 3, 4 ] ]

3. Using the Vector class:

Maybe in your case, it would be more helpful to operate with a class Vector:

class Vector {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }
}

const coordinatesStorage = [];

coordinatesStorage.push(new Vector(1, 2));
coordinatesStorage.push(new Vector(3, 4));
coordinatesStorage.push(new Vector(4, 6));

And here in the console you will see [ Vector { x: 1, y: 2 }, Vector { x: 3, y: 4}, Vector { x: 4, y: 6 } ]

Take a look at the Vector implementations in JS:

1. https://gist.github.com/jjgrainger/808640fcb5764cf92c3cad960682c677

2. https://github.com/maxkueng/victor/blob/master/index.js

I hope this helps. Good luck!