JavaScript: Draw a right-angled triangle

Last update on May 30 2022 10:02:40 (UTC/GMT +8 hours)

JavaScript Drawing: Exercise-4 with Solution

Write a JavaScript program to draw the following right-angled triangle.

Sample output:

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Draw a right-angled triangle</title>
</head>
<body onload="draw();">
<canvas id="canvas" width="150" height="150"></canvas>
</body>
</html>

JavaScript Code:

function draw() 
{
  var canvas = document.getElementById('canvas');
  if (canvas.getContext)
  {
    var context = canvas.getContext('2d');

    context.beginPath();
    context.moveTo(75,75);
    context.lineTo(10,75);
    context.lineTo(10,25);
    context.fill();
  }
}

Live Demo:

See the Pen javascript-drawing-exercise-4 by w3resource (@w3resource) on CodePen.

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Next: Write a JavaScript program to draw the following diagram [use moveto() function].

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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