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In this article we will see how to draw a line in a Loop or cycle in HTML5; specifically, with the Canvas API; Although the Canvas API already offers primitives to draw a line (lineTo()), in this exercise we will paint a line from squares; of variable sizes, which will be the "pixels" that make up our line; To draw a square we will use the following function:

ctx.fillRect(X,Y,Width,Height);

X: The X coordinate of the top left corner of the rectangle.
Y: The Y coordinate of the top left corner of the rectangle.
Width: Width of the rectangle in pixels.
Height: Length of the rectangle in pixels.

Drawing the line with the Canvas API

We define the size of the Canvas in pixels; the Canvas is going to be a square:

var tamCanvas = 360;

The next thing is to define how many "pixels" the line will consist of and their size:

var numCuadrados = 10;
var tam = 100;

Now we need to define the spacing between the "pixels"; which will be smaller as we increase the number of rectangles:

var espaciado = (tamCanvas-tam)/(numCuadrados-1);

Now we perform a cycle where we will draw the "pixels" that will make up the line:

for(var i=0; i <numCuadrados; i++){
    ctx.fillStyle = "rgba(255, 255, 255, 0.8)"; 
    ctx.fillRect(i*espaciado, i*espaciado, tam, tam);
}

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Final score

Interactive example

If you have doubts about the operation of the previous parameters, in this example you can vary the value of each parameter:

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