# Get distance between two points in canvas

JavascriptCanvas## Javascript Problem Overview

I have canvas drawing tab and want lineWidth to be based on distance between two last mousemove coordinate updates. I will make translation of distance to width myself, I just need to know how to get distance between those points (I already have coordinates of those pointes).

## Javascript Solutions

## Solution 1 - Javascript

You can do it with pythagoras theorem

If you have two points (x1, y1) and (x2, y2) then you can calculate the difference in x and difference in y, lets call them a and b.

```
var a = x1 - x2;
var b = y1 - y2;
var c = Math.sqrt( a*a + b*b );
// c is the distance
```

## Solution 2 - Javascript

Note that `Math.hypot`

is part of the ES2015 standard. There's also a good polyfill on the MDN doc for this feature.

So getting the distance becomes as easy as `Math.hypot(x2-x1, y2-y1)`

.

## Solution 3 - Javascript

http://en.wikipedia.org/wiki/Euclidean_distance

If you have the coordinates, use the formula to calculate the distance:

```
var dist = Math.sqrt( Math.pow((x1-x2), 2) + Math.pow((y1-y2), 2) );
```

If your platform supports the `**`

operator, you can instead use that:

```
const dist = Math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2);
```

## Solution 4 - Javascript

To find the distance between 2 points, you need to find the length of the hypotenuse in a right angle triangle with a width and height equal to the vertical and horizontal distance:

```
Math.hypot(endX - startX, endY - startY)
```

## Solution 5 - Javascript

The distance between two coordinates x and y! x1 and y1 is the first point/position, x2 and y2 is the second point/position!

```
function diff (num1, num2) {
if (num1 > num2) {
return (num1 - num2);
} else {
return (num2 - num1);
}
};
function dist (x1, y1, x2, y2) {
var deltaX = diff(x1, x2);
var deltaY = diff(y1, y2);
var dist = Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
return (dist);
};
```

## Solution 6 - Javascript

i tend to use this calculation a lot in things i make, so i like to add it to the Math object:

```
Math.dist=function(x1,y1,x2,y2){
if(!x2) x2=0;
if(!y2) y2=0;
return Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
}
Math.dist(0,0, 3,4); //the output will be 5
Math.dist(1,1, 4,5); //the output will be 5
Math.dist(3,4); //the output will be 5
```

**Update:**

this approach is especially happy making when you end up in situations something akin to this (i often do):

```
varName.dist=Math.sqrt( ( (varName.paramX-varX)/2-cx )*( (varName.paramX-varX)/2-cx ) + ( (varName.paramY-varY)/2-cy )*( (varName.paramY-varY)/2-cy ) );
```

that horrid thing becomes the much more manageable:

```
varName.dist=Math.dist((varName.paramX-varX)/2, (varName.paramY-varY)/2, cx, cy);
```

## Solution 7 - Javascript

Here's a quick one-liner to find the distance between `(x1, y1)`

and `(x2, y2)`

```
const distance = (x1, y1, x2, y2) => Math.hypot(x2 - x1, y2 - y1);
```

Here is a short runnable demo:

const distance = (x1, y1, x2, y2) => Math.hypot(x2 - x1, y2 - y1);

```
var x1 = 1
var y1 = 5
var x2 = 4
var y2 = 5
var d = distance(x1, y1, x2, y2)
console.log(`The distance between (${x1}, ${y1}) and (${x2}, ${y2}) is ${d}`)
```