access object variable within array javascript

Question

I have an array that holds 'particle' objects, with each particle taking parameters; x position, y position, angle of projection, and velocity.

I am trying to access the x and y positions for each particle within the array to perform further calculations, but I am having trouble with the syntax. Here is a brief summary of the code:

var Particle( x, y , angle, velocity) {            
// here the implementation of the dynamics of the particles are coded 
}
     
// here 100 random particle objects 
// are pushed to the array
   var particleArray = [];
    
for(var i =0; i < 100; i++){

particleArray.push(new Particle( 
               (Math.random()* ( innerWidth  - radius*2) + radius), 
               (Math.random()* ( innerHeight - radius*2) + radius), 
               Math.PI*Math.random(), 5 ))      
}

now I want to try and access one of the components , for example: the x position of the 47th particle in the array, but I am having trouble like I said above with the syntax or if I have even approached this problem correctly.

var Particle( x, y , angle, velocity) { is invalid syntax, try var Particle = function( x, y , angle, velocity) { — Rob M.
– Rob M., Commented Jan 24, 2018 at 20:40

TimoStaudinger · Accepted Answer · 2018-01-24 20:41:34Z

2

You can access the n-th object in the array via the square bracket notation (note that arrays are 0-indexed): [n-1].

Then you can access a certain property via the dot notation: object.property.

var x = particleArray[46].x

answered Jan 24, 2018 at 20:41

TimoStaudinger

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GregX999 · Accepted Answer · 2018-01-24 20:42:27Z

1

You should be able to access the x position 47th particle with particleArray[46].x. (Since arrays are "zero-indexed", the first particle is particleArray[0], the second is particleArray[1], etc.)

answered Jan 24, 2018 at 20:42

GregX999

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Andam · Accepted Answer · 2018-01-24 20:48:49Z

0

Here is a simple example.

Note that array in javascript are zero based index (first position is zero not one) hence 47th is index 46

var particles = [];
var innerWidth = 10;
var innerHeight = 5;
var radius = 2;

function Particle(x, y, angle, velocity){
  this.x = x;
  this.y = y;
  this.angle = angle;
  this.velocity = velocity;
}

function generateParticles(numberOfParticles){
  var tempParticles = [];
  for(var i = 0; i < numberOfParticles; i++){
    tempParticles.push(
      new Particle( 
          ( Math.random() * (innerWidth - radius * 2) + radius) ,
          ( Math.random() * ( innerHeight - radius * 2) + radius) ,
          Math.PI*Math.random(),
          5 
        )
      );
  }
  return tempParticles;
}

particles = generateParticles(100);
console.log(particles[46])

answered Jan 24, 2018 at 20:48

Andam

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1 Comment

user9263921 Over a year ago

Thats similar to what I have, but i appreciate the help!

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