JavaScript: Draw a diagram with diagonal, white to black circles

Last update on May 30 2022 10:01:13 (UTC/GMT +8 hours)

JavaScript Drawing : Exercise-6 with Solution

Write a JavaScript program to draw the following diagram [diagonal, white to black circles].

Sample output:

Sample Solution:

HTML Code:

<!DOCTYPE html>
  <html>
  <head>
  <title>Diagonal, White to Black circles</title>
  </head>
 <body>
  <canvas id="myCanvas" width="1500" height="800">
  <p>Update your browser!</p>
  </canvas>
  </body> 
  </html>

JavaScript Code:

function draw()
  {
  var ctx = document.getElementById("myCanvas").getContext("2d");
  var counter = 0;
  for (var i=0;i<6;i++)
  {
  for (var j=0;j<6;j++)
  {
  //Start from white and goes to black
  ctx.fillStyle = "rgb(" + Math.floor(255-42.5*i) + "," + Math.floor(255-42.5*i) +
  "," + Math.floor(255-42.5*j) + ")";
ctx.beginPath();
  if (i === counter && j === counter)
  {
  //creates the circles
  ctx.arc(25+j*50,30+i*50,20,0,Math.PI*2,true);
  ctx.fill();
  //creates a border around the circles so white one will be vissible

  ctx.stroke();
  } 
  }
  counter++;
  }
  }
  draw();

Live Demo:

See the Pen javascript-drawing-exercise-6 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

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Next: Javascript Object Exercises

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04