fix(transparentize): float alpha value to 2 decimals

Ensures transparentize alpha values are floated 2 decimals.

fix #548

Author: bhough

package.json

@@ -1,6 +1,6 @@
 {
   "name": "polished",
-  "version": "4.0.3",
+  "version": "4.0.4",
   "description": "A lightweight toolset for writing styles in Javascript.",
   "license": "MIT",
   "author": "Brian Hough <[email protected]> (https://polished.js.org)",

src/color/test/transparentize.test.js

@@ -54,6 +54,10 @@ describe('transparentize', () => {
     expect(transparentize(-0.5, 'rgba(255, 0, 0, .8)')).toEqual('#f00')
   })
 
+  it('should properly round a float to 2 decimals.', () => {
+    expect(transparentize(0.55, '#01B0BB')).toEqual('rgba(1,176,187,0.45)')
+  })
+
   it('should reduce the opacity when passed a string for amount', () => {
     expect(transparentize('0.1', '#fff')).toEqual('rgba(255,255,255,0.9)')
   })

src/color/transparentize.js

@@ -37,7 +37,7 @@ function transparentize(amount: number | string, color: string): string {
   const alpha: number = typeof parsedColor.alpha === 'number' ? parsedColor.alpha : 1
   const colorWithAlpha = {
     ...parsedColor,
-    alpha: guard(0, 1, (alpha * 100 - parseFloat(amount) * 100) / 100),
+    alpha: guard(0, 1, +(alpha * 100 - parseFloat(amount) * 100).toFixed(2) / 100),
   }
   return rgba(colorWithAlpha)
 }