Draw polygonal line with a looping

Hi all

I drew polygon line with canvas before, code example as below:

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var ctx = canvas.getContext("2d");
ctx.beginPath();

ctx.moveTo(0,126);

{ data in loop }
    ctx.lineTo(x , {{data}});
{ endfor }

ctx.stroke();
ctx.closePath();
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Set "moveto" one time and using "lineto" with a looping.

Now I change to the SVG, and want to do that again.

But after reading document it seems can not.

For example:

if I use "path" : <path d="M150 0 L75 200 L225 200 Z" />
I need decide "moveto" and "lineto" point at the same time.

if I use "line":
<line x1="0" y1="0" x2="300" y2="300"
style="stroke:rgb(99,99,99);stroke-width:2"/>

same does "line".

So how should I can draw  a polygonal line with a looping ?