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.

• guest271314: Where does the code at Question get an array element?
• Rob M.: var Particle( x, y , angle, velocity) { is invalid syntax, try var Particle = function( x, y , angle, velocity) {

Answer 1

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

Answer 2

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.)

Answer 3

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])

• user9263921: Thats similar to what I have, but i appreciate the help!